scholarly journals Adaptive Robust Force Position Control for Flexible Active Prosthetic Knee Using Gait Trajectory

2020 ◽  
Vol 10 (8) ◽  
pp. 2755
Author(s):  
Fang Peng ◽  
Haiyang Wen ◽  
Cheng Zhang ◽  
Bugong Xu ◽  
Jiehao Li ◽  
...  
Keyword(s):  
Time Delay ◽  
Position Control ◽  
Control Method ◽  
Hybrid Control ◽  
Sliding Mode ◽  
Impedance Control ◽  
Joint Stiffness ◽  
Variable Stiffness ◽  
Time Delay Estimation ◽  
Model Free

Active prosthetic knees (APKs) are widely used in the past decades. However, it is still challenging to make them more natural and controllable because: (1) most existing APKs that use rigid actuators have difficulty obtaining more natural walking; and (2) traditional finite-state impedance control has difficulty adjusting parameters for different motions and users. In this paper, a flexible APK with a compact variable stiffness actuator (VSA) is designed for obtaining more flexible bionic characteristics. The VSA joint is implemented by two motors of different sizes, which connect the knee angle and the joint stiffness. Considering the complexity of prothetic lower limb control due to unknown APK dynamics, as well as strong coupling between biological joints and prosthetic joints, an adaptive robust force/position control method is designed for generating a desired gait trajectory of the prosthesis. It can operate without the explicit model of the system dynamics and multiple tuning parameters of different gaits. The proposed model-free scheme utilizes the time-delay estimation technique, sliding mode control, and fuzzy neural network to realize finite-time convergence and gait trajectory tracking. The virtual prototype of APK was established in ADAMS as a testing platform and compared with two traditional time-delay control schemes. Some demonstrations are illustrated, which show that the proposed method has superior tracking characteristics and stronger robustness under uncertain disturbances within the trajectory error in ± 0 . 5 degrees. The VSA joint can reduce energy consumption by adjusting stiffness appropriately. Furthermore, the feasibility of this method was verified in a human–machine hybrid control model.

Robust position control of hydraulic manipulators using time delay estimation and nonsingular fast terminal sliding mode

2017 ◽  
Vol 232 (1) ◽  
pp. 50-61 ◽  
Author(s):  
Xichang Liang ◽  
Yi Wan ◽  
Chengrui Zhang ◽  
Yanyun Kou ◽  
Qianqian Xin ◽  
...  
Keyword(s):  
Time Delay ◽  
Position Control ◽  
Sliding Mode ◽  
Time Delay Estimation ◽  
Tracking Performance ◽  
Delay Estimation ◽  
Terminal Sliding Mode ◽  
Model Free ◽  
Fast Terminal Sliding Mode ◽  
Hydraulic Manipulator

A simple and robust tracking controller based on time delay estimation and nonsingular fast terminal sliding mode is proposed for the position control of hydraulic manipulator. The proposed controller does not require the mathematical model of hydraulic manipulator dynamics, which ensures that the method is simple and model free. Two elements, time delay estimation and nonsingular fast terminal sliding mode, are implemented in the proposed controller. Time delay estimation estimates the complex dynamics of the hydraulic manipulator, and nonsingular fast terminal sliding mode is implemented as the nonlinear desired error dynamic to ensure fast convergence and high trajectory tracking accuracy. Experiments are performed to verify the tracking performance of the method on a hydraulic manipulator. The results demonstrate that this method achieves faster and higher precision position tracking performance than a conventional time delay control with linear error dynamics.

scholarly journals Fractional Order Adaptive Fast Super-Twisting Sliding Mode Control for Steer-by-Wire Vehicles with Time-Delay Estimation

Electronics ◽  
2021 ◽  
Vol 10 (19) ◽  
pp. 2424
Author(s):  
Yong Yang ◽  
Yunbing Yan ◽  
Xiaowei Xu
Keyword(s):  
Time Delay ◽  
Sliding Mode Control ◽  
Fractional Order ◽  
Sliding Mode ◽  
Time Delay Estimation ◽  
Lyapunov Theory ◽  
Delay Estimation ◽  
Mode Control ◽  
Model Free ◽  
Steer By Wire

It is difficult to model and determine the parameters of the steer-by-wire (SBW) system accurately, and the perturbation is variable with complex and changeable tire–road conditions. In order to improve the control performance of the vehicle SBW system, an adaptive fast super-twisting sliding mode control (AFST-SMC) scheme with time-delay estimation (TDE) is proposed. The proposed scheme uses TDE to acquire the lumped dynamics in a simple way and establishes a practical model-free structure. Then, a fractional order (FO) sliding mode surface and a fast super-twisting sliding mode control structure were designed on the basic super-twisting sliding mode to ensure fast convergence and high control accuracy. Since the uncertain boundary information of the actual system is unknown, a novel adaptive algorithm is proposed to regulate the control gain based on the control errors. Theoretical analysis concerning system stability is given based on the Lyapunov theory. Finally, the effectiveness of the method is verified through comparative experiments. The results show that the proposed TDE-AFST-FOSMC control scheme has the advantages of model-free, fast response and high accuracy.

Robotic Impedance Control with Fuzzy Sliding Model Control Strategy

2014 ◽  
Vol 598 ◽  
pp. 605-609
Author(s):  
Shiuh Jer Huang ◽  
Chiao Kuen Yu ◽  
You Min Huang
Keyword(s):  
Hybrid Control ◽  
Sliding Mode ◽  
Impedance Control ◽  
Robotic Assembly ◽  
Robotic Control ◽  
Model Free ◽  
Model Control ◽  
Force Profile ◽  
Fuzzy Sliding Mode ◽  
Fuzzy Sliding Model Control

During robotic assembly and interactive applications, the robot end-effector must follow a motion trajectory and exert an appropriate force profile against the contacted environment to provide a specified dynamic working compliance. It is a difficult control problem. Here, an embedded robotic control structure is constructed and the related hybrid control software programs are developed. The model-free intelligent fuzzy sliding mode controller is introduced to design force and position controllers, respectively for hybrid impedance control purpose. The experimental results are provided to demonstrate the effectiveness of the proposed hybrid impedance control system.

scholarly journals A Time Delay Estimation Based Adaptive Sliding Mode Strategy for Hybrid Impedance Control

IEEE Access ◽  
2020 ◽  
Vol 8 ◽  
pp. 155352-155361
Author(s):  
Madan Mohan Rayguru ◽  
Mohan Rajesh Elara ◽  
Braulio Felix Gomez ◽  
Balakrishnan Ramalingam
Keyword(s):  
Time Delay ◽  
Sliding Mode ◽  
Impedance Control ◽  
Time Delay Estimation ◽  
Delay Estimation ◽  
Adaptive Sliding Mode

scholarly journals A light cable-driven manipulator developed for aerial robots: Structure design and control research

2020 ◽  
Vol 17 (3) ◽  
pp. 172988142092642
Author(s):  
Yaoyao Wang ◽  
Rui Zhang ◽  
Feng Ju ◽  
Jinbo Zhao ◽  
Bai Chen ◽  
...  
Keyword(s):  
Time Delay ◽  
Sliding Mode ◽  
Time Delay Estimation ◽  
Delay Estimation ◽  
Sliding Mode Controller ◽  
Moving Mass ◽  
Terminal Sliding Mode ◽  
Aerial Robots ◽  
Model Free ◽  
Nonsingular Terminal Sliding Mode

To effectively reduce the mass and simplify the structure of traditional aerial manipulators, we propose novel light cable-driven manipulator for the aerial robots in this article. The drive motors and corresponding reducers are removed from the joints to the base; meanwhile, force and motion are transmitted remotely through cables. Thanks to this design, the moving mass has been greatly reduced. In the meantime, the application of cable-driven technology also brings about extra difficulties for high-precise control of cable-driven manipulators. Hence, we design a nonsingular terminal sliding mode controller using time-delay estimation. The time-delay estimation is applied to obtain lumped system dynamics and found an attractive model-free scheme, while the nonsingular terminal sliding mode controller is utilized to enhance the control performance. Stability is analyzed based on Lyapunov theory. Finally, the designed light cable-driven manipulator and presented time-delay estimation-based nonsingular terminal sliding mode controller are analyzed. Corresponding results show that (1) our proposed cable-driven manipulator has high load to mass ratio of 0.8 if we only consider the moving mass and (2) our proposed time-delay estimation-based nonsingular terminal sliding mode is model-free and can provide higher accuracy than the widely used time-delay estimation-based proportional–derivative (PD) controller.

Comparing model-based control methods for simultaneous stiffness and position control of inflatable soft robots

2020 ◽  
pp. 027836492091196
Author(s):  
Charles M. Best ◽  
Levi Rupert ◽  
Marc D. Killpack
Keyword(s):  
Dynamic Models ◽  
Position Control ◽  
Sliding Mode ◽  
Joint Stiffness ◽  
Variable Stiffness ◽  
Soft Robots ◽  
End Effector ◽  
Simultaneous Control ◽  
Stiffness Model ◽  
Stiffness Control

Inflatable robots are naturally lightweight and compliant, which may make them well suited for operating in unstructured environments or in close proximity to people. The inflatable joints used in this article consist of a strong fabric exterior that constrains two opposing compliant air bladders that generate torque (unlike McKibben actuators where pressure changes cause translation). This antagonistic structure allows the simultaneous control of position and stiffness. However, dynamic models of soft robots that allow variable stiffness control have not been well developed. In this work, a model that includes stiffness as a state variable is developed and validated. Using the stiffness model, a sliding mode controller and model predictive controller are developed to control stiffness and position simultaneously. For sliding mode control (SMC), the joint stiffness was controlled to within 0.07 Nm/rad of a 45 Nm/rad command. For model predictive control (MPC) the joint stiffness was controlled to within 0.045 Nm/rad of the same stiffness command. Both SMC and MPC were able to control to within 0.5° of a desired position at steady state. Stiffness control was extended to a multiple-degree-of-freedom soft robot using MPC. Controlling stiffness of a 4-DOF arm reduced the end-effector deflection by approximately 50% (from 17.9 to 12.2cm) with a 4 lb (1.8 kg) step input applied at the end effector when higher joint stiffness (40 Nm/rad) was used compared with low stiffness (30 Nm/rad). This work shows that the derived stiffness model can enable effective position and stiffness control.

Joint space tracking control of underwater vehicle-manipulator systems using continuous nonsingular fast terminal sliding mode

2017 ◽  
Vol 232 (4) ◽  
pp. 448-458 ◽  
Author(s):  
Yaoyao Wang ◽  
Bai Chen ◽  
Hongtao Wu
Keyword(s):  
Time Delay ◽  
Tracking Control ◽  
Sliding Mode ◽  
Underwater Vehicle ◽  
Time Delay Estimation ◽  
Delay Estimation ◽  
Control Performance ◽  
Terminal Sliding Mode ◽  
Model Free ◽  
Fast Terminal Sliding Mode

To ensure satisfactory control performance for the underwater vehicle-manipulator systems, a novel continuous nonsingular fast terminal sliding mode controller is proposed and investigated using time delay estimation in this article. Complex lumped unknown dynamics including the strong nonlinear couplings and external disturbance are properly compensated with time delay estimation, which are mainly based on the time-delayed signals of underwater vehicle-manipulator systems and can provide with a fascinating model-free feature. Afterwards, the satisfactory tracking control performance and good robustness under heavy lumped uncertainties are ensured using the continuous nonsingular fast terminal sliding mode term with a fast terminal sliding mode–type reaching law. Therefore, the proposed controller is easy to use thanks to time delay estimation, and can ensure good control performance owing to continuous nonsingular fast terminal sliding mode. Stability of the closed-loop control system is analyzed using Lyapunov stability theory, and theoretical tracking errors are calculated and presented. Finally, the effectiveness and advantages of the proposed controller are demonstrated through comparative 7-degree-of-freedom pool experiments.

Model-free robust finite-time force tracking control for piezoelectric actuators using time-delay estimation with adaptive fuzzy compensator

2019 ◽  
Vol 42 (3) ◽  
pp. 351-364
Author(s):  
Shengzheng Kang ◽  
Hongtao Wu ◽  
Xiaolong Yang ◽  
Yao Li ◽  
Yaoyao Wang
Keyword(s):  
Time Delay ◽  
Finite Time ◽  
Sliding Mode ◽  
Piezoelectric Actuators ◽  
Time Delay Estimation ◽  
Delay Estimation ◽  
Terminal Sliding Mode ◽  
Adaptive Fuzzy ◽  
Model Free ◽  
Force Tracking

A robust and practical force control system is crucial to the sensitive piezo-driven micromanipulation applications. This paper presents a new model-free robust finite-time force tracking controller for piezoelectric actuators (PEAs). The proposed controller composes of three intuitive terms: (1) a time-delay estimation (TDE) term that eliminates the requirement of detailed information about the PEA system, realizing model-free control; (2) a fast integral terminal sliding mode-based desired error dynamics injection term that ensures fast convergence and high tracking precision; (3) a correcting term based on adaptive fuzzy logic system that compensates for TDE errors caused by discontinuous nonlinearities and improves the robustness of the system. Force differential signal used in the controller is estimated online by a force state estimator. Stability of the closed-loop system and finite-time convergence are analyzed in theory. Comparative experiments are carried out on a PEA system with two superposed PEAs. Results show that the proposed control strategy has faster convergence, higher tracking accuracy and stronger robustness compared with the traditional TDE-based force controllers.

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