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Gehlhar R, Tucker M, Young AJ, Ames AD. A Review of Current State-of-the-Art Control Methods for Lower-Limb Powered Prostheses. ANNUAL REVIEWS IN CONTROL 2023; 55:142-164. [PMID: 37635763 PMCID: PMC10449377 DOI: 10.1016/j.arcontrol.2023.03.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/29/2023]
Abstract
Lower-limb prostheses aim to restore ambulatory function for individuals with lower-limb amputations. While the design of lower-limb prostheses is important, this paper focuses on the complementary challenge - the control of lower-limb prostheses. Specifically, we focus on powered prostheses, a subset of lower-limb prostheses, which utilize actuators to inject mechanical power into the walking gait of a human user. In this paper, we present a review of existing control strategies for lower-limb powered prostheses, including the control objectives, sensing capabilities, and control methodologies. We separate the various control methods into three main tiers of prosthesis control: high-level control for task and gait phase estimation, mid-level control for desired torque computation (both with and without the use of reference trajectories), and low-level control for enforcing the computed torque commands on the prosthesis. In particular, we focus on the high- and mid-level control approaches in this review. Additionally, we outline existing methods for customizing the prosthetic behavior for individual human users. Finally, we conclude with a discussion on future research directions for powered lower-limb prostheses based on the potential of current control methods and open problems in the field.
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Affiliation(s)
- Rachel Gehlhar
- Department of Mechanical and Civil Engineering, California Institute of Technology, 1200 E. California Blvd., Pasadena, 91125, CA, USA
| | - Maegan Tucker
- Department of Mechanical and Civil Engineering, California Institute of Technology, 1200 E. California Blvd., Pasadena, 91125, CA, USA
| | - Aaron J Young
- Woodruff School of Mechanical Engineering, Georgia Institute of Technology, North Avenue, Atlanta, 30332, GA, USA
- Institute for Robotics and Intelligent Machines, Georgia Institute of Technology, North Avenue, Atlanta, 30332, GA, USA
| | - Aaron D Ames
- Department of Mechanical and Civil Engineering, California Institute of Technology, 1200 E. California Blvd., Pasadena, 91125, CA, USA
- Department of Computing and Mathematical Sciences, California Institute of Technology, 1200 E. California Blvd., Pasadena, 91125, CA, USA
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2
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Kouzbary HA, Kouzbary MA, Tham LK, Liu J, Shasmin HN, Abu Osman NA. Generating an Adaptive and Robust Walking Pattern for a Prosthetic Ankle-Foot by Utilizing a Nonlinear Autoregressive Network With Exogenous Inputs. IEEE TRANSACTIONS ON NEURAL NETWORKS AND LEARNING SYSTEMS 2022; 33:6297-6305. [PMID: 33979293 DOI: 10.1109/tnnls.2021.3076060] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
One of the major challenges in developing powered lower limb prostheses is emulating the behavior of an intact lower limb with different walking speeds over diverse terrains. Numerous studies have been conducted on control algorithms in the field of rehabilitation robotics to achieve this overarching goal. Recent studies on powered prostheses have frequently used a hierarchical control scheme consisting of three control levels. Most control structures have at least one element of discrete transition properties that requires numerous sensors to improve classification accuracy, consequently increasing computational load and costs. In this study, we proposed a user-independent and free-mode method for eliminating the need to switch among different controllers. We constructed a database by using four OPAL wearable devices (Mobility Lab, APDM Inc., USA) for seven able-bodied subjects. We recorded the gait of each subject at three ambulation speeds during ground-level walking to train a nonlinear autoregressive network with an exogenous input recurrent neural network (NARX RNN) to estimate foot orientation (angular position) in the sagittal plane using shank angular velocity as external input. The trained NARX RNN estimated the foot orientation of all the subjects at different walking speeds over flat terrain with an average root-mean-square error (RMSE) of 2.1° ± 1.7°. The minimum correlation between the estimated and measured values was 86%. Moreover, a t-test showed that the error was normally distributed with a high certainty level (0.88 minimum p -value).
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3
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Horn JC, Gregg RD. Nonholonomic Virtual Constraints for Control of Powered Prostheses Across Walking Speeds. IEEE TRANSACTIONS ON CONTROL SYSTEMS TECHNOLOGY : A PUBLICATION OF THE IEEE CONTROL SYSTEMS SOCIETY 2022; 30:2062-2071. [PMID: 35990403 PMCID: PMC9390073 DOI: 10.1109/tcst.2021.3133823] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
This paper presents a method to design a nonholonomic virtual constraint (NHVC) controller that produces multiple distinct stance-phase trajectories for corresponding walking speeds. NHVCs encode velocity-dependent joint trajectories via momenta conjugate to the unactuated degree(s)-of-freedom of the system. We recently introduced a method for designing NHVCs that allow for stable bipedal robotic walking across variable terrain slopes. This work extends the notion of NHVCs for application to variable-cadence powered prostheses. Using the segmental conjugate momentum for the prosthesis, an optimization problem is used to design a single stance-phase NHVC for three distinct walking speed trajectories (slow, normal, and fast). This stance-phase controller is implemented with a holonomic swing phase controller on a powered knee-ankle prosthesis, and experiments are conducted with an able-bodied user walking in steady and non-steady velocity conditions. The control scheme is capable of representing 1) multiple, task-dependent reference trajectories, and 2) walking gait variance due to both temporal and kinematic changes in user motion.
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Affiliation(s)
- Jonathan C Horn
- Department of Mechanical Engineering and Department of Bioengineering, University of Texas at Dallas, Richardson, TX 75080, USA
| | - Robert D Gregg
- Department of Electrical Engineering and Computer Science and the Robotics Institute, University of Michigan, Ann Arbor, MI 48109 USA
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4
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Gehlhar R, Yang JH, Ames AD. Powered Prosthesis Locomotion on Varying Terrains: Model-Dependent Control With Real-Time Force Sensing. IEEE Robot Autom Lett 2022. [DOI: 10.1109/lra.2022.3154810] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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5
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Naeem A, Rizwan M, Farhan Maqbool H, Ahsan M, Raza A, Abouhossein A, Ali Dehghani-Sanij A. Virtual constraint control of Knee-Ankle prosthesis using an improved estimate of the thigh phase-variable. Biomed Signal Process Control 2022. [DOI: 10.1016/j.bspc.2021.103366] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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6
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Event-Based, Intermittent, Discrete Adaptive Control for Speed Regulation of Artificial Legs. ACTUATORS 2021. [DOI: 10.3390/act10100264] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
For artificial legs that are used in legged robots, exoskeletons, and prostheses, it suffices to achieve velocity regulation at a few key instants of swing rather than tight trajectory tracking. Here, we advertise an event-based, intermittent, discrete controller to enable set-point regulation for problems that are traditionally posed as trajectory following. We measure the system state at prior-chosen instants known as events (e.g., vertically downward position), and we turn on the controller intermittently based on the regulation errors at the set point. The controller is truly discrete, as these measurements and controls occur at the time scale of the system to be controlled. To enable set-point regulation in the presence of uncertainty, we use the errors to tune the model parameters. We demonstrate the method in the velocity control of an artificial leg, a simple pendulum, with up to 50% mass uncertainty. Starting with a 100% regulation error, we achieve velocity regulation of up to 10% in about five swings with only one measurement per swing.
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7
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Hong W, Anil Kumar N, Hur P. A Phase-Shifting Based Human Gait Phase Estimation for Powered Transfemoral Prostheses. IEEE Robot Autom Lett 2021. [DOI: 10.1109/lra.2021.3068907] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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8
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Elery T, Rezazadeh S, Nesler C, Gregg RD. Design and Validation of a Powered Knee-Ankle Prosthesis with High-Torque, Low-Impedance Actuators. IEEE T ROBOT 2020; 36:1649-1668. [PMID: 33299386 PMCID: PMC7720653 DOI: 10.1109/tro.2020.3005533] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
We present the design of a powered knee-ankle prosthetic leg, which implements high-torque actuators with low-reduction transmissions. The transmission coupled with a high-torque and low-speed motor creates an actuator with low mechanical impedance and high backdrivability. This style of actuation presents several possible benefits over modern actuation styles in emerging robotic prosthetic legs, which include free-swinging knee motion, compliance with the ground, negligible unmodeled actuator dynamics, less acoustic noise, and power regeneration. Benchtop tests establish that both joints can be backdriven by small torques (~1-3 Nm) and confirm the small reflected inertia. Impedance control tests prove that the intrinsic impedance and unmodeled dynamics of the actuator are sufficiently small to control joint impedance without torque feedback or lengthy tuning trials. Walking experiments validate performance under the designed loading conditions with minimal tuning. Lastly, the regenerative abilities, low friction, and small reflected inertia of the presented actuators reduced power consumption and acoustic noise compared to state-of-art powered legs.
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Affiliation(s)
- Toby Elery
- T. Elery is with the Departments of Bioengineering and Mechanical Engineering, University of Texas at Dallas, Richardson, TX 75080 USA. S. Rezazadeh is with the Department of Mechanical Engineering, University of Denver, Denver, CO, 80208 USA. C. Nesler and R. D. Gregg are with the Department of Electrical Engineering and Computer Science; Robotics Institute, University of Michigan, Ann Arbor, MI, 48109 USA
| | - Siavash Rezazadeh
- T. Elery is with the Departments of Bioengineering and Mechanical Engineering, University of Texas at Dallas, Richardson, TX 75080 USA. S. Rezazadeh is with the Department of Mechanical Engineering, University of Denver, Denver, CO, 80208 USA. C. Nesler and R. D. Gregg are with the Department of Electrical Engineering and Computer Science; Robotics Institute, University of Michigan, Ann Arbor, MI, 48109 USA
| | - Christopher Nesler
- T. Elery is with the Departments of Bioengineering and Mechanical Engineering, University of Texas at Dallas, Richardson, TX 75080 USA. S. Rezazadeh is with the Department of Mechanical Engineering, University of Denver, Denver, CO, 80208 USA. C. Nesler and R. D. Gregg are with the Department of Electrical Engineering and Computer Science; Robotics Institute, University of Michigan, Ann Arbor, MI, 48109 USA
| | - Robert D Gregg
- T. Elery is with the Departments of Bioengineering and Mechanical Engineering, University of Texas at Dallas, Richardson, TX 75080 USA. S. Rezazadeh is with the Department of Mechanical Engineering, University of Denver, Denver, CO, 80208 USA. C. Nesler and R. D. Gregg are with the Department of Electrical Engineering and Computer Science; Robotics Institute, University of Michigan, Ann Arbor, MI, 48109 USA
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9
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Kumar S, Mohammadi A, Quintero D, Rezazadeh S, Gans N, Gregg RD. Extremum Seeking Control for Model-Free Auto-Tuning of Powered Prosthetic Legs. IEEE TRANSACTIONS ON CONTROL SYSTEMS TECHNOLOGY : A PUBLICATION OF THE IEEE CONTROL SYSTEMS SOCIETY 2020; 28:2120-2135. [PMID: 33041615 PMCID: PMC7546444 DOI: 10.1109/tcst.2019.2928514] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
This paper proposes an extremum seeking controller (ESC) for simultaneously tuning the feedback control gains of a knee-ankle powered prosthetic leg using continuous-phase controllers. Previously, the proportional gains of the continuous-phase controller for each joint were tuned manually by trial-and-error, which required several iterations to achieve a balance between the prosthetic leg tracking error performance and the user's comfort. In this paper, a convex objective function is developed, which incorporates these two goals. We present a theoretical analysis demonstrating that the quasi-steady-state value of the objective function is independent of the controller damping gains. Furthermore, we prove the stability of error dynamics of continuous-phase controlled powered prosthetic leg along with ESC dynamics using averaging and singular perturbation tools. The developed cost function is then minimized by ESC in real-time to simultaneously tune the proportional gains of the knee and ankle joints. The optimum of the objective function shifts at different walking speeds, and our algorithm is suitably fast to track these changes, providing real-time adaptation for different walking conditions. Benchtop and walking experiments verify the effectiveness of the proposed ESC across various walking speeds.
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Affiliation(s)
- Saurav Kumar
- Department of Electrical Engineering and the Department of Bioengineering, University of Texas at Dallas, Richardson, TX 75080 USA
| | - Alireza Mohammadi
- Department of Electrical and Computer Engineering, University of Michigan-Dearborn, Dearborn, MI 48128 USA
| | - David Quintero
- Department of Mechanical Engineering, San Francisco State University, San Francisco, CA 94132 USA
| | - Siavash Rezazadeh
- Department of Bioengineering, University of Texas at Dallas, Richardson, TX 75080 USA
| | - Nicholas Gans
- University of Texas at Arlington Research Institute, University of Texas at Arlington, Fort Worth, TX 76118 USA
| | - Robert D Gregg
- Department of Electrical Engineering and Computer Science and the Robotics Institute, University of Michigan, Ann Arbor, MI 48109 USA
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10
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Yeatman M, Lv G, Gregg RD. Decentralized Passivity-Based Control With a Generalized Energy Storage Function for Robust Biped Locomotion. JOURNAL OF DYNAMIC SYSTEMS, MEASUREMENT, AND CONTROL 2019; 141:1010071-10100711. [PMID: 31666751 PMCID: PMC6611352 DOI: 10.1115/1.4043801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2018] [Revised: 05/14/2019] [Indexed: 06/10/2023]
Abstract
This paper details a decentralized passivity-based control (PBC) to improve the robustness of biped locomotion in the presence of gait-generating external torques and parametric errors in the biped model. Previous work demonstrated a passive output for biped systems based on a generalized energy that, when directly used for feedback control, increases the basin of attraction and convergence rate of the biped to a stable limit cycle. This paper extends the concept with a theoretical framework to address both uncertainty in the biped model and a lack of sensing hardware, by allowing the designer to neglect arbitrary states and parameters in the system. This framework also allows the control to be implemented on wearable devices, such as a lower limb exoskeleton or powered prosthesis, without needing a model of the user's dynamics. Simulations on a six-link biped model demonstrate that the proposed control scheme increases the convergence rate of the biped to a walking gait and improves the robustness to perturbations and to changes in ground slope.
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Affiliation(s)
- Mark Yeatman
- Department of Mechanical Engineering, University of Texas at Dallas, Richardson, TX 75080
| | - Ge Lv
- Department of Electrical Engineering, University of Texas at Dallas, Richardson, TX 75080
| | - Robert D Gregg
- Department of Bioengineering;Department of Mechanical Engineering,University of Texas at Dallas, Richardson, TX 75080 e-mail:
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11
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Mohammadi A, Gregg RD. Variable Impedance Control of Powered Knee Prostheses Using Human-Inspired Algebraic Curves. JOURNAL OF COMPUTATIONAL AND NONLINEAR DYNAMICS 2019; 14:101007-10100710. [PMID: 32280314 PMCID: PMC7104744 DOI: 10.1115/1.4043002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Revised: 02/23/2019] [Indexed: 06/11/2023]
Abstract
Achieving coordinated motion between transfemoral amputee patients and powered prosthetic joints is of paramount importance for powered prostheses control. In this article, we propose employing an algebraic curve representation of nominal human walking data for a powered knee prosthesis controller design. The proposed algebraic curve representation encodes the desired holonomic relationship between the human and the powered prosthetic joints with no dependence on joint velocities. For an impedance model of the knee joint motion driven by the hip angle signal, we create a continuum of equilibria along the gait cycle using a variable impedance scheme. Our variable impedance-based control law, which is designed using the parameter-dependent Lyapunov function framework, realizes the coordinated hip-knee motion with a family of spring and damper behaviors that continuously change along the human-inspired algebraic curve. In order to accommodate variability in the user's hip motion, we propose a computationally efficient radial projection-based algorithm onto the human-inspired algebraic curve in the hip-knee plane.
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Affiliation(s)
- Alireza Mohammadi
- Department of Electrical and Computer Engineering, The University of Michigan, Dearborn, MI 48128
| | - Robert D. Gregg
- Department of Bioengineering, The University of Texas at Dallas, Richardson, TX 75080; Department of Mechanical Engineering, The University of Texas at Dallas, Richardson, TX 75080
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12
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Fevre M, Goodwine B, Schmiedeler JP. Terrain-blind walking of planar underactuated bipeds via velocity decomposition-enhanced control. Int J Rob Res 2019. [DOI: 10.1177/0278364919870242] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In this article, we develop and assess a novel approach for the control of underactuated planar bipeds that is based on velocity decomposition. The new controller employs heuristic rules that mimic the functionality of transverse linearization feedback control and that can be layered on top of a conventional hybrid zero dynamics (HZD)-based controller. The heuristics sought to retain HZD-based control’s simplicity and enhance disturbance rejection for practical implementation on realistic biped robots. The proposed control strategy implements a feedback on the time rate of change of the decomposed uncontrolled velocity and is compared with conventional HZD-based control and transverse linearization feedback control for both vanishing and non-vanishing disturbances. Simulation studies with a point-foot, three-link biped show that the proposed method has nearly identical performance to transverse linearization feedback control and outperforms conventional HZD-based control. For the non-vanishing case, the velocity decomposition-enhanced controller outperforms HZD-based control, but takes fewer steps on average before failure than transverse linearization feedback control when walking on uneven terrain without visual perception of the ground. The findings were validated experimentally on a planar, five-link biped robot for eight different uneven terrains. The velocity decomposition-enhanced controller outperformed HZD-based control while maintaining a relatively low specific energetic cost of transport (~0.45). The biped robot “blindly” traversed uneven terrains with changes in terrain height accumulating to 5% of its leg length using the stand-alone low-level controller.
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13
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Elery T, Rezazadeh S, Nesler C, Doan J, Zhu H, Gregg RD. Design and Benchtop Validation of a Powered Knee-Ankle Prosthesis with High-Torque, Low-Impedance Actuators. IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION : ICRA : [PROCEEDINGS]. IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION 2019; 2018:2788-2795. [PMID: 30598854 DOI: 10.1109/icra.2018.8461259] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
This paper describes the design of a powered knee- and-ankle transfemoral prosthetic leg, which implements high torque density actuators with low-reduction transmissions. The low reduction of the transmission coupled with a high-torque and low-speed motor creates an actuator with low mechanical impedance and high backdrivability. This style of actuation presents several possible benefits over modern actuation styles implemented in emerging robotic prosthetic legs. Such benefits include free-swinging knee motion, compliance with the ground, negligible unmodeled actuator dynamics, and greater potential for power regeneration. Benchtop validation experiments were conducted to verify some of these benefits. Backdrive and free-swinging knee tests confirm that both joints can be backdriven by small torques (~3 Nm). Bandwidth tests reveal that the actuator is capable of achieving frequencies required for walking and running. Lastly, open-loop impedance control tests prove that the intrinsic impedance and unmodeled dynamics of the actuator are sufficiently small to control joint impedance without torque feedback.
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Affiliation(s)
- Toby Elery
- Departments of Bioengineering, Mechanical Engineering, and Electrical and Computer Engineering, University of Texas at Dallas, Richardson, TX 75080 USA
| | - Siavash Rezazadeh
- Departments of Bioengineering, Mechanical Engineering, and Electrical and Computer Engineering, University of Texas at Dallas, Richardson, TX 75080 USA
| | - Christopher Nesler
- Departments of Bioengineering, Mechanical Engineering, and Electrical and Computer Engineering, University of Texas at Dallas, Richardson, TX 75080 USA
| | - Jack Doan
- Departments of Bioengineering, Mechanical Engineering, and Electrical and Computer Engineering, University of Texas at Dallas, Richardson, TX 75080 USA
| | - Hanqi Zhu
- Departments of Bioengineering, Mechanical Engineering, and Electrical and Computer Engineering, University of Texas at Dallas, Richardson, TX 75080 USA
| | - Robert D Gregg
- Departments of Bioengineering, Mechanical Engineering, and Electrical and Computer Engineering, University of Texas at Dallas, Richardson, TX 75080 USA
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14
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Mohammadi A, Fakoorian S, Horn JC, Simon D, Gregg RD. Hybrid Nonlinear Disturbance Observer Design for Underactuated Bipedal Robots. PROCEEDINGS OF THE ... IEEE CONFERENCE ON DECISION & CONTROL. IEEE CONFERENCE ON DECISION & CONTROL 2018; 2018:1217-1224. [PMID: 30778276 PMCID: PMC6377174 DOI: 10.1109/cdc.2018.8618650] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Existence of disturbances in unknown environments is a pervasive challenge in robotic locomotion control. Disturbance observers are a class of unknown input observers that have been extensively used for disturbance rejection in numerous robotics applications. In this paper, we extend a class of widely-used nonlinear disturbance observers to underactuated bipedal robots, which are controlled using hybrid zero dynamics-based control schemes. The proposed hybrid nonlinear disturbance observer provides the autonomous biped robot control system with disturbance rejection capabilities, while the underlying hybrid zero-dynamics based control law remains intact.
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Affiliation(s)
- Alireza Mohammadi
- Departments of Bioengineering and Mechanical Engineering at the University of Texas,
| | - Seyed Fakoorian
- Department of Electrical & Computer Engineering, Cleveland State University, Ohio,
| | - Jonathan C Horn
- Departments of Bioengineering and Mechanical Engineering at the University of Texas,
| | - Dan Simon
- Department of Electrical & Computer Engineering, Cleveland State University, Ohio,
| | - Robert D Gregg
- Departments of Bioengineering and Mechanical Engineering at the University of Texas,
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15
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Kumar S, Mohammadi A, Gans N, Gregg RD. Automatic Tuning of Virtual Constraint-Based Control Algorithms for Powered Knee-Ankle Prostheses. FIRST ANNUAL IEEE CONFERENCE ON CONTROL TECHNOLOGY AND APPLICATIONS : CCTA 2017 : KOHALA COAST, HAWAI'I, AUGUST 27-30, 2017. IEEE CONFERENCE ON CONTROL TECHNOLOGY AND APPLICATIONS (1ST : 2017 : WAIMEA, HAWAII ISLAND, HAWAII) 2018; 2017:812-818. [PMID: 30175324 DOI: 10.1109/ccta.2017.8062560] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
State-of-art powered prosthetic legs are often controlled using a collection of joint impedance controllers designed for different phases of a walking cycle. Consequently, finite state machines are used to control transitions between different phases. This approach requires a large number of impedance parameters and switching rules to be tuned. Since one set of control parameters cannot be used across different amputees, clinicians spend enormous time tuning these gains for each patient. This paper proposes a virtual constraint-based control scheme with a smaller set of control parameters, which are automatically tuned in real-time using an extremum seeking controller (ESC). ESC, being a model-free control method, assumes no prior knowledge of either the prosthesis or human. Using a singular perturbation analysis, we prove that the virtual constraint tracking errors are small and the PD gains remain bounded. Simulations demonstrate that our ESC-based method is capable of adapting the virtual-constraint based control parameters for amputees with different masses.
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Affiliation(s)
- Saurav Kumar
- Department of Electrical Engineering, University of Texas at Dallas, Richardson, TX 75080, USA.,Department of Bioengineering, University of Texas at Dallas, Richardson, TX 75080, USA
| | - Alireza Mohammadi
- Department of Bioengineering, University of Texas at Dallas, Richardson, TX 75080, USA.,Department of Mechanical Engineering, University of Texas at Dallas, Richardson, TX 75080, USA
| | - Nicholas Gans
- Department of Electrical Engineering, University of Texas at Dallas, Richardson, TX 75080, USA
| | - Robert D Gregg
- Department of Bioengineering, University of Texas at Dallas, Richardson, TX 75080, USA.,Department of Mechanical Engineering, University of Texas at Dallas, Richardson, TX 75080, USA
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16
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Mohammadi A, Gregg RD. HUMAN-INSPIRED ALGEBRAIC CURVES FOR WEARABLE ROBOT CONTROL. PROCEEDINGS OF THE ASME DYNAMIC SYSTEMS AND CONTROL CONFERENCE. ASME DYNAMIC SYSTEMS AND CONTROL CONFERENCE 2018; 2018:V001T11A002;. [PMID: 30906619 PMCID: PMC6424523 DOI: 10.1115/dscc2018-9061] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Having unified representations of human walking gait data is of paramount importance for wearable robot control. In the rehabilitation robotics literature, control approaches that unify the gait cycle of wearable robots are more appealing than the conventional approaches that rely on dividing the gait cycle into several periods, each with their own distinct controllers. In this article we propose employing algebraic curves to represent human walking data for wearable robot controller design. In order to generate algebraic curves from human walking data, we employ the 3L fitting algorithm, a tool developed in the pattern recognition literature for fitting implicit polynomial curves to given datasets. For an impedance model of the knee joint motion driven by the hip angle signal, we provide conditions by which the generated algebraic curves satisfy a robust relative degree condition throughout the entire walking gait cycle. The robust relative degree property makes the algebraic curve representation of walking gaits amenable to various nonlinear output tracking controller design techniques.
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Affiliation(s)
- Alireza Mohammadi
- Dept. Bioengineering and Dept. Mechanical Engineering, The University of Texas at Dallas, Richardson, Texas 75080,
| | - Robert D Gregg
- Dept. Bioengineering and Dept. Mechanical Engineering, The University of Texas at Dallas, Richardson, Texas 75080,
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17
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Quintero D, Villarreal DJ, Lambert DJ, Kapp S, Gregg RD. Continuous-Phase Control of a Powered Knee-Ankle Prosthesis: Amputee Experiments Across Speeds and Inclines. IEEE T ROBOT 2018; 34:686-701. [PMID: 30008623 PMCID: PMC6042879 DOI: 10.1109/tro.2018.2794536] [Citation(s) in RCA: 93] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Control systems for powered prosthetic legs typically divide the gait cycle into several periods with distinct controllers, resulting in dozens of control parameters that must be tuned across users and activities. To address this challenge, this paper presents a control approach that unifies the gait cycle of a powered knee-ankle prosthesis using a continuous, user-synchronized sense of phase. Virtual constraints characterize the desired periodic joint trajectories as functions of a phase variable across the entire stride. The phase variable is computed from residual thigh motion, giving the amputee control over the timing of the prosthetic joint patterns. This continuous sense of phase enabled three transfemoral amputee subjects to walk at speeds from 0.67 to 1.21 m/s and slopes from -2.5 to +9.0 deg. Virtual constraints based on task-specific kinematics facilitated normative adjustments in joint work across walking speeds. A fixed set of control gains generalized across these activities and users, which minimized the configuration time of the prosthesis.
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Affiliation(s)
- David Quintero
- Department of Bioengineering, University of Texas at Dallas, Richardson, TX 75080 USA
- Department of Mechanical Engineering, University of Texas at Dallas, Richardson, TX 75080 USA
| | - Dario J Villarreal
- Department of Electrical Engineering, Southern Methodist University, Dallas, TX 75275 USA
| | - Daniel J Lambert
- Department of Electrical and Computer Engineering, University of Texas at Dallas, Richardson, TX 75080 USA
| | - Susan Kapp
- Department of Rehabilitation Medicine, University of Washington, Seattle, WA 98104 USA
| | - Robert D Gregg
- Department of Bioengineering, University of Texas at Dallas, Richardson, TX 75080 USA
- Department of Mechanical Engineering, University of Texas at Dallas, Richardson, TX 75080 USA
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Quintero D, Martin AE, Gregg RD. Toward Unified Control of a Powered Prosthetic Leg: A Simulation Study. IEEE TRANSACTIONS ON CONTROL SYSTEMS TECHNOLOGY : A PUBLICATION OF THE IEEE CONTROL SYSTEMS SOCIETY 2018; 26:305-312. [PMID: 29403259 PMCID: PMC5796555 DOI: 10.1109/tcst.2016.2643566] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
This brief presents a novel control strategy for a powered knee-ankle prosthesis that unifies the entire gait cycle, eliminating the need to switch between controllers during different periods of gait. A reduced-order Discrete Fourier Transformation (DFT) is used to define virtual constraints that continuously parameterize periodic joint patterns as functions of a mechanical phasing variable. In order to leverage the provable stability properties of Hybrid Zero Dynamics (HZD), hybrid-invariant Bézier polynomials are converted into unified DFT virtual constraints for various walking speeds. Simulations of an amputee biped model show that the unified prosthesis controller approximates the behavior of the original HZD design under ideal scenarios and has advantages over the HZD design when hybrid invariance is violated by mismatches with the human controller. Two implementations of the unified virtual constraints, a feedback linearizing controller and a more practical joint impedance controller, produce similar results in simulation.
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Affiliation(s)
- David Quintero
- Departments of Bioengineering and Mechanical Engineering, University of Texas at Dallas, Richardson, TX 75080. A.E
| | - Anne E Martin
- Department of Mechanical and Nuclear Engineering, Pennsylvania State University, State College, PA 16801
| | - Robert D Gregg
- Departments of Bioengineering and Mechanical Engineering, University of Texas at Dallas, Richardson, TX 75080. A.E
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Massalin Y, Abdrakhmanova M, Varol HA. User-Independent Intent Recognition for Lower Limb Prostheses Using Depth Sensing. IEEE Trans Biomed Eng 2017; 65:1759-1770. [PMID: 29989950 DOI: 10.1109/tbme.2017.2776157] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
OBJECTIVE The intent recognizers of advanced lower limb prostheses utilize mechanical sensors on the prosthesis and/or electromyographic measurements from the residual limb. Besides the delay caused by these signals, such systems require user-specific databases to train the recognizers. In this paper, our objective is the development and validation of a user-independent intent recognition framework utilizing depth sensing. METHODS We collected a depth image dataset from 12 healthy subjects engaging in a variety of routine activities. After filtering the depth images, we extracted simple features employing a recursive strategy. The feature vectors were classified using a support vector machine. For robust activity mode switching, we implemented a voting filter scheme. RESULTS The model selection showed that the support vector machine classifier with no dimension reduction has the highest classification accuracy. Specifically, it reached 94.1% accuracy on the testing data from four subjects. We also observed a positive trend in the accuracy of classifiers trained with data from increasing the number of subjects. Activity mode switching using a voting filter detected 732 out of 778 activity mode transitions of the four users while initiating 70 erroneous transitions during steady-state activities. CONCLUSION The intent recognizer trained on multiple subjects can be used for any other subject, providing a promising solution for supervisory control of powered lower limb prostheses. SIGNIFICANCE A user-independent intent recognition framework has the potential to decrease or eliminate the time required for extensive data collection regiments for intent recognizer training. This could accelerate the introduction of robotic lower limb prostheses to the market.
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Villarreal DJ, Quintero D, Gregg RD. Piecewise and unified phase variables in the control of a powered prosthetic leg. IEEE Int Conf Rehabil Robot 2017; 2017:1425-1430. [PMID: 28814020 DOI: 10.1109/icorr.2017.8009448] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Many control methods have been proposed for powered prosthetic legs, ranging from finite state machines that switch between discrete phases of gait to unified controllers that have a continuous sense of phase. In particular, recent work has shown that a mechanical phase variable can parameterize the entire gait cycle for controlling a prosthetic leg during steady rhythmic locomotion. However, the unified approach does not provide voluntary control over non-rhythmic motions like stepping forward and back. In this paper we present a phasing algorithm that uses the amputee's hip angle to control both rhythmic and non-rhythmic motion through two modes: 1) a piecewise (PW) function that provides users voluntary control over stance and swing in a piecewise manner, and 2) a unified function that continuously synchronizes the motion of the prosthetic leg with the amputee user at different walking speeds. The two phase variable approaches are compared in experiments with a powered knee-ankle prosthesis used by an above-knee amputee subject.
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Mohammadi A, Horn J, Gregg RD. Removing Phase Variables from Biped Robot Parametric Gaits. CONTROL TECHNOLOGY AND APPLICATIONS. CONTROL TECHNOLOGY AND APPLICATIONS 2017; 2017:834-840. [PMID: 30198027 DOI: 10.1109/ccta.2017.8062563] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Hybrid zero dynamics-based control is a promising framework for controlling underactuated biped robots and powered prosthetic legs. In this control paradigm, stable walking gaits are implicitly encoded in polynomial output functions of the robot configuration variables, which are to be zeroed via feedback. The biped output functions are parameterized by a suitable mechanical phasing variable whose evolution determines the biped gait progression during each step. Determining a proper phase variable, however, might not always be a trivial task. In this paper, we present a method for generating output functions from given parametric walking gaits without any explicit knowledge of the phase variables. Our elimination method is based on computing the resultant of polynomials, an algebraic tool widely used in computer algebra.
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Affiliation(s)
- Alireza Mohammadi
- Department of Mechanical Engineering, University of Texas at Dallas, 800 West Campbell Road, Richardson, TX 75080-3021.,Department of Bioengineering, University of Texas at Dallas, 800 West Campbell Road, Richardson, TX 75080-3021
| | - Jonathan Horn
- Department of Mechanical Engineering, University of Texas at Dallas, 800 West Campbell Road, Richardson, TX 75080-3021.,Department of Bioengineering, University of Texas at Dallas, 800 West Campbell Road, Richardson, TX 75080-3021
| | - Robert D Gregg
- Department of Mechanical Engineering, University of Texas at Dallas, 800 West Campbell Road, Richardson, TX 75080-3021.,Department of Bioengineering, University of Texas at Dallas, 800 West Campbell Road, Richardson, TX 75080-3021
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Martin AE, Villarreal DJ, Gregg RD. Characterizing and modeling the joint-level variability in human walking. J Biomech 2016; 49:3298-3305. [PMID: 27594679 DOI: 10.1016/j.jbiomech.2016.08.015] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Revised: 08/15/2016] [Accepted: 08/15/2016] [Indexed: 11/18/2022]
Abstract
Although human gait is often assumed to be periodic, significant variability exists. This variability appears to provide different information than the underlying periodic signal, particularly about fall risk. Most studies on variability have either used step-to-step metrics such as stride duration or point-wise standard deviations, neither of which explicitly capture the joint-level variability as a function of time. This work demonstrates that a second-order Fourier series for stance joints and a first-order Fourier series for swing joints can accurately capture the variability in joint angles as a function of time on a per-step basis for overground walking at the self-selected speed. It further demonstrates that a total of seven normal distributions, four linear relationships, and twelve continuity constraints can be used to describe how the Fourier series vary between steps. The ability of the proposed method to create curves that match human joint-level variability was evaluated both qualitatively and quantitatively using randomly generated curves.
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Affiliation(s)
- Anne E Martin
- Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA16802, USA.
| | - Dario J Villarreal
- Department of Bioengineering, University of Texas at Dallas, Richardson, TX 75080, USA.
| | - Robert D Gregg
- Department of Bioengineering, University of Texas at Dallas, Richardson, TX 75080, USA; Department of Mechanical Engineering, University of Texas at Dallas, Richardson, TX 75080, USA.
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