Sliding Mode Impedance and Stiffness Control of a Pneumatic Cylinder

2019 ◽  
Author(s):  
Jonathon E. Slightam ◽  
Eric J. Barth ◽  
Mark L. Nagurka
Keyword(s):  
Motion Control ◽  
Sliding Mode ◽  
Impedance Control ◽  
Pneumatic Cylinder ◽  
Control Methods ◽  
Control Applications ◽  
Compliant Motion ◽  
Simultaneous Control ◽  
Stiffness Control ◽  
Virtual Impedance

Abstract Pneumatic double acting cylinders are able to provide inherent stiffness and force control for compliant motion control applications. Impedance control methods allow for a broad spectrum of mechanical properties of actuators to be achieved. The range of this spectrum can be increased by simultaneously controlling the actuator’s inherent stiffness and impedance, a concept explored in this paper. Presented here is a sliding mode impedance and stiffness controller for a servo-pneumatic double acting cylinder. Two proportional servo-valves are employed for simultaneous control of the virtual impedance and inherent stiffness of the pneumatic cylinder. Experimental results of tracking trajectories and contact are reported and discussed with respect to different approaches in the literature.

scholarly journals Consensus Control for Reactive Power Sharing Using an Adaptive Virtual Impedance Approach

Energies ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 2026 ◽  
Author(s):  
Ahmed S. Alsafran ◽  
Malcolm W. Daniels
Keyword(s):  
Rate Of Convergence ◽  
Reactive Power ◽  
Impedance Control ◽  
Power Sharing ◽  
Control Methods ◽  
Triangle Mesh ◽  
Secondary Control ◽  
Consensus Control ◽  
Communication Topology ◽  
Virtual Impedance

Reactive power sharing among distributed generators (DGs) in islanded microgrids (MGs) presents control challenges, particularly in the mismatched feeder line condition. Improved droop control methods independently struggle to resolve this issue and centralized secondary control methods exhibit a high risk of collapse for the entire MG system under any failure in the central control. Distributed secondary control methods have been recently proposed to mitigate the reactive power error evident in the presence of mismatched feeder lines. This paper details a mathematical model of an adaptive virtual impedance control that is based on both leaderless and leader-followers consensus controls with a novel triangle mesh communication topology to ensure accurate active and reactive power sharing. The approach balances an enhanced rate of convergence with the anticipated implementation cost. A MATLAB/Simulink model with six DG units validates the proposed control performance under three different communication structures: namely, ring, complete, and triangle mesh topologies. The results suggest that leaderless consensus control is a reliable option with large DG systems, while the leader-followers consensus control is suitable for the small systems. The triangle mesh communication topology provides a compromise approach balancing the rate of convergence and the expected cost. The extensibility and scalability are advantages of this topology over the alternate ring and complete topologies.

Simultaneous Learning of Robot Impedance Parameters Using Neural Networks

2007 ◽  
Vol 19 (1) ◽  
pp. 106-113
Author(s):  
Mutsuhiro Terauchi ◽  
◽  
Yoshiyuki Tanaka ◽  
Seishiro Sakaguchi ◽  
Nan Bu ◽  
...  
Keyword(s):  
Neural Networks ◽  
Computer Simulations ◽  
Impedance Control ◽  
Robotic Manipulator ◽  
Effective Control ◽  
Control Methods ◽  
Learning Method ◽  
Conventional Methods ◽  
Impedance Parameters ◽  
Virtual Impedance

Impedance control is one of the most effective control methods for interaction between a robotic manipulator and its environment. Robot impedance control regulates the response of the manipulator to contact and virtual impedance control regulates the manipulator's response before contact. Although these impedance parameters may be regulated using neural networks, conventional methods do not consider regulating robot impedance and virtual impedance simultaneously. This paper proposes a simultaneous learning method to regulate the impedance parameters using neural networks. The validity of the proposed method is demonstrated in computer simulations of tasks by a multi-joint robotic manipulator.

Motion control methods for X-rudder underwater vehicles: Model based sliding Mode and non-model based iterative sliding mode

2020 ◽  
Vol 216 ◽  
pp. 108054
Author(s):  
Wenjin Wang ◽  
Yingkai Xia ◽  
Ying Chen ◽  
Guohua Xu ◽  
Zhongxiang Chen ◽  
...  
Keyword(s):  
Motion Control ◽  
Sliding Mode ◽  
Underwater Vehicles ◽  
Control Methods ◽  
Model Based

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.

scholarly journals A Compact Adjustable Stiffness Rotary Actuator Based on Linear Springs: Working Principle, Design, and Experimental Verification

Actuators ◽  
2020 ◽  
Vol 9 (4) ◽  
pp. 141
Author(s):  
Cong Phat Vo ◽  
Van Du Phan ◽  
Thanh Ha Nguyen ◽  
Kyoung Kwan Ahn
Keyword(s):  
Elastic Energy ◽  
Sliding Mode ◽  
Fast Transient Response ◽  
Output Torque ◽  
Rotary Actuator ◽  
Simultaneous Control ◽  
Sliding Mode Controllers ◽  
Output Element ◽  
Working Principle ◽  
Stiffness Control

Inspired by improving the adaptive capability of the robot to external impacts or shocks, the adjustable stiffness behavior in joints is investigated to ensure conformity with the safety index. This paper proposes a new soft actuation unit, namely Adjustable Stiffness Rotary Actuator (ASRA), induced by a novel optimization of the elastic energy in an adjusting stiffness mechanism. Specifically, a stiffness transmission is configured by three pairs of antagonistically linear springs with linkage bars. The rotational disk and link bars assist the simplified stiffness control based on a linear transmission. To enhance the elastic energy efficiency, the force compressions of the linear springs are set to be perpendicular to the three-spoke output element, i.e., the output link direction. Besides, the ASRA model is also formed to investigate the theoretical capabilities of the stiffness output and passive energy. As a simulated result, a high passive energy storage ability can be achieved. Then, several experimental scenarios are performed with integral sliding mode controllers to verify the physical characteristics of the ASRA. As trial results, the fast transient response and high accuracy of both the position and stiffness tracking tests are expressed, in turn, independent and simultaneous control cases. Moreover, the real output torque is measured to investigate its reflecting stiffness.

Development of an Active Worktable and Its Application to Force Control of Robot Manipulators

2000 ◽  
Vol 12 (3) ◽  
pp. 249-253
Author(s):  
Shin-ichi Nakajima ◽  
Keyword(s):  
Force Control ◽  
Degrees Of Freedom ◽  
Control Method ◽  
Robot Manipulator ◽  
Impedance Control ◽  
Robot Manipulators ◽  
Compliant Motion ◽  
Stiffness Control

An active worktable, which can be applied to force control tasks of commercial robot manipulators, has been designed and built. The active worktable has several degrees of freedom and accommodates its position/force in accordance with the motion of a robot manipulator. A stiffness control method and an impedance control method are implemented in the active worktable to achieve compliant motion. Several experiments were carried out to confirm basic effectiveness of the active worktable.

Motion Control and Design of an Aerial Robotic System

2006 ◽  
Author(s):  
Mehdi Nikkhah ◽  
Hashem Ashrafiuon ◽  
Edmond J. Dougherty
Keyword(s):  
Motion Control ◽  
Vibration Mode ◽  
Sliding Mode ◽  
Three Dimensional ◽  
Robotic System ◽  
Electric Motors ◽  
Fundamental Vibration ◽  
Simultaneous Control ◽  
Dynamics And Control ◽  
And Control

This research examines the dynamics and control of an aerial robotic system to determine its feasibility and general design features. The robotic system consists of a cable driven trolley and a camera platform suspended and controlled by six cables designed in a configuration similar to the Stewart platform. The camera and trolley cables are driven through winches controlled by electric motors. An algorithm is developed based on the sliding mode approach to simultaneous control the trolley trajectory and the full three-dimensional camera linear and rotational motion. Trolley cable flexibility and fundamental vibration mode is included in the analysis though not directly controlled at this stage. Wind forces are also included in the model as unknown but bound disturbances. A working prototype of the system has also been developed and its general features are introduced in this paper.

Impedance Control Based Sliding Mode for Lower Limb Rehabilitation Robot

2014 ◽  
Vol 672-674 ◽  
pp. 1770-1773 ◽  
Author(s):  
Fu Cheng Cao ◽  
Li Min Du
Keyword(s):  
Dynamic Response ◽  
Sliding Mode Control ◽  
Lower Limb ◽  
Control Method ◽  
Sliding Mode ◽  
Impedance Control ◽  
Rehabilitation Robot ◽  
Active Rehabilitation ◽  
Limb Rehabilitation ◽  
Lower Limb Rehabilitation

Aimed at improving the dynamic response of the lower limb for patients, an impedance control method based on sliding mode was presented to implement an active rehabilitation. Impedance control can achieve a target-reaching training without the help of a therapist and sliding mode control has a robustness to system uncertainty and vary limb strength. Simulations demonstrate the efficacy of the proposed method for lower limb rehabilitation.

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