Precise dynamic modeling of pneumatic muscle actuators with modified Bouw–Wen hysteresis model

2021 ◽  
pp. 095440892110080
Author(s):  
Mohammad Sheikh Sofla ◽  
Mohammad Zareinejad
Keyword(s):  
Weight Ratio ◽  
Muscle Length ◽  
Control Procedure ◽  
Force Model ◽  
Hysteresis Model ◽  
Restoring Force ◽  
Pneumatic Muscle ◽  
Hysteresis Nonlinearity ◽  
Asymmetric Force ◽  
Muscle Actuators

Pneumatic muscle actuators (PMAs) are frequently used in a wide variety of biorobotic applications, such as robotic orthoses and wearable exoskeletons, due to their high power/weight ratio and significant compliance. However, the asymmetric hysteresis nonlinearity reduces their fidelity and cause difficulties in the accurate control procedure. In this paper, Bouc–Wen hysteresis model is modified to describe the asymmetric force/length hysteresis of the PMA. The effect of muscle length on hysteretic restoring force is considered in this modified model and experimental results show that the proposed model has a better performance to characterize the asymmetric hysteresis loop of pneumatic muscles. The nonlinear pressure/force model of these actuators also is modeled precisely and its performance is experimentally verified for different muscle lengths.

scholarly journals Active Motion Control of a Knee Exoskeleton Driven by Antagonistic Pneumatic Muscle Actuators

Actuators ◽  
2020 ◽  
Vol 9 (4) ◽  
pp. 134
Author(s):  
Wei Zhao ◽  
Aiguo Song
Keyword(s):  
Sliding Mode ◽  
Weight Ratio ◽  
Practical Application ◽  
Active Motion ◽  
Pneumatic Muscle ◽  
The Past ◽  
Robotic Devices ◽  
Muscle Actuators ◽  
Further Development ◽  
Rehabilitation Robotic

The pneumatic muscle actuator (PMA) has been widely applied in the researches of rehabilitation robotic devices for its high power to weight ratio and intrinsic compliance in the past decade. However, the high nonlinearity and hysteresis behavior of PMA limit its practical application. Hence, the control strategy plays an important role in improving the performance of PMA for the effectiveness of rehabilitation devices. In this paper, a PMA-based knee exoskeleton based on ergonomics is proposed. Based on the designed knee exoskeleton, a novel proxy-based sliding mode control (PSMC) is introduced to obtain the accurate trajectory tracking. Compared with conventional control approaches, this new PSMC can obtain better performance for the designed PMA-based exoskeleton. Experimental results indicate good tracking performance of this controller, which provides a good foundation for the further development of assist-as-needed training strategies in gait rehabilitation.

scholarly journals A New Approach to Modeling and Controlling a Pneumatic Muscle Actuator-Driven Setup Using Back Propagation Neural Networks

Complexity ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Jun Zhong ◽  
Xu Zhou ◽  
Minzhou Luo
Keyword(s):  
Back Propagation ◽  
Weight Ratio ◽  
Adaptive Controller ◽  
Back Propagation Neural Network ◽  
Sampled Data ◽  
Nonlinear Characteristics ◽  
New Approach ◽  
Pneumatic Muscle ◽  
Muscle Actuators

Pneumatic muscle actuators (PMAs) own excellent compliance and a high power-to-weight ratio and have been widely used in bionic robots and rehabilitated robots. However, the high nonlinear characteristics of PMAs due to inherent construction and pneumatic driving principle bring great challenges in applications acquired accurately modeling and controlling. To tackle the tricky problem, a single PMA mass setup is constructed, and a back propagation neural network (BPNN) is employed to identify the dynamics of the setup. An offline model is built up using sampled data, and online modifications are performed to further improve the quality of the model. An adaptive controller based on BPNN is designed using gradient descent information of the built-up model. Experiments of identifying the PMA setup using BPNN and position tracking by adaptive BPNN controller are performed, and results demonstrate the good capacity in accurate controlling of the PMA setup.

Experimental Comparisons of Sliding Mode Controlled Pneumatic Muscle and Cylinder Actuators

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
Ville Jouppila ◽  
S. Andrew Gadsden ◽  
Asko Ellman
Keyword(s):  
Sliding Mode ◽  
Weight Ratio ◽  
Industrial Applications ◽  
Stick Slip ◽  
Servo Systems ◽  
Pneumatic Muscle ◽  
Positioning Systems ◽  
Actuation System ◽  
Highly Nonlinear ◽  
Muscle Actuators

Pneumatic muscle actuators offer a higher force-to-weight ratio compared to traditional cylinder actuators, and introduce stick-slip-free operation that offers an interesting option for positioning systems. Despite several advantages, pneumatic muscle actuators are commonly avoided in industrial applications, mainly due to rather different working principles. Due to the highly nonlinear characteristics of the muscle actuator and pneumatic system, a reliable control strategy is required. Although muscle actuators are widely studied, the literature lacks detailed studies where the performance for servo systems is compared with traditional pneumatic cylinders. In this paper, a pneumatic servo actuation system is compared with a traditional cylinder actuator. As the overall system dynamics are highly nonlinear and not well defined, a sliding mode control (SMC) strategy is chosen for the control action. In order to improve the tracking performance, an SMC strategy with an integral action (SMCI) is also implemented. The control algorithms are experimentally applied on the pneumatic muscle and the cylinder actuator, for the purposes of position tracking. The robustness of the systems are verified and compared by varying the applied loads.

Static Force Model-Based Stiffness Model for Pneumatic Muscle Actuators

2015 ◽  
Vol 18 ◽  
pp. 207-214 ◽  
Author(s):  
József Sárosi ◽  
Ján Piteľ ◽  
Jaroslav Šeminský
Keyword(s):  
Variable Stiffness ◽  
Relative Displacement ◽  
Time Variable ◽  
Force Model ◽  
Power Weight ◽  
Static Force ◽  
Pneumatic Muscle ◽  
Stiffness Model ◽  
Muscle Actuators ◽  
And Control

Pneumatic muscle actuators (PMAs) differ from general pneumatic systems as they have no inner moved parts and there is no sliding on the surfaces. During action they reach high velocities, while the power/weight and power/volume rations reach high levels. The main drawbacks of PMAs are limited contraction (relative displacement), nonlinear and time variable behaviour, existence of hysteresis and step-jump pressure (to start radial diaphragm deformation) and also antagonistic connection of PMAs to generate two-direction motion. These make PMAs difficult to modelling and control. In this paper a new stiffness model and the variable-stiffness spring-like characteristics are described and tested using two Fluidic Muscles made by Festo Company. The muscles have the same diameter, but different length.

scholarly journals Evaluation of MRI-compatible pneumatic muscle stepper motors

2019 ◽  
Vol 5 (1) ◽  
pp. 339-341
Author(s):  
Robert Odenbach ◽  
Alan Guthrie ◽  
Michael Friebe
Keyword(s):  
Low Cost ◽  
Muscle Length ◽  
Engineering Industry ◽  
Stepper Motor ◽  
Pneumatic Muscle ◽  
Metal Free ◽  
Pneumatic Muscles ◽  
Stepper Motors ◽  
Robotic Devices ◽  
Muscle Actuators

AbstractThe automation of instruments and tools (e.g. bone drill) or robotic devices (e.g. needle positioning robot for prostate surgery) for use in interventional MRI (iMRI) is still challenging due to a lack of accurate, affordable and completely metal-free actuators and motors. Inspired by biological muscles, a bionic equivalent known as the fluid muscle actuator (which can be operated pneumatically or hydraulically) is well-known in the mechanical engineering industry. Fluid muscle actuators have multiple beneficial characteristics: they are simple, self-returning, low-friction and can produce relatively high actuation forces at low diameters and pressures. We present two novel designs for metal-free, pneumatic stepper motors for potential application in iMRI. Our stepper motors are powered by simple pneumatic muscles, which are assembled from low-cost off-the-shelf components. Besides, the components of the stepper motor demonstrators were 3Dprinted using a stereolithographic additive manufacturing process (SLA printing). We evaluate the effect of pneumatic muscle length on contractile force and length. Our results demonstrated the functional feasibility of the pneumatic muscle-powered and fully MRI-compatible stepper motor designs. In a next step, we will optimize the motor´s design, characterize their performance and reliability, and use the stepper motors to power a micropositioning device in iMRI-phantom tests.

Multiplexed Force Control of Pneumatic Muscles

2006 ◽  
Author(s):  
V. Jouppila ◽  
A. Ellman
Keyword(s):  
High Power ◽  
Force Control ◽  
Weight Ratio ◽  
Pressure Control ◽  
Pneumatic Actuators ◽  
Pneumatic Muscle ◽  
Servo Valve ◽  
Highly Nonlinear ◽  
Muscle Actuators ◽  
Pneumatic Cylinders

Pneumatic actuators are often used in applications that require high power-to-weight ratio, combined with low price and clean and fast operation. However, due to the compressibility of air and highly nonlinear behavior of seal friction, the position and force control of these actuators is difficult to manage. As a result, pneumatic cylinders have been used for many years solely in simple repetitive tasks requiring only a very limited amount of system control. Nonetheless, the pneumatic actuators have properties such as compactness, high power-to-weight ratio, and simplicity that are desirable features in advanced robotics. To overcome the shortcomings, a number of advanced pneumatic components have been developed, of which the most promising is the pneumatic muscle. Compared to a cylinder, a pneumatic muscle not only has a higher power-to-weight and power-to-volume ratio but it is also almost frictionless and has zero leakage. In spite of the muscle actuator's nonlinear force-to-contraction characteristics, many motion and force control methods have been successfully applied to it. The characteristics of the actuator enable it to be used in simple positioning systems and as a variable gas spring. The actuator's almost linear pressure-to-force ratio is extremely well-suited to a variety of gripping and pressing applications. Due to the muscle actuator's characteristics and recent developments in pneumatic valve technology, there is an opportunity to share a single pressure control servo valve among multiple muscle actuators. The multiplexed control of the actuators with only one servo valve reduces the system costs significantly. In this paper we investigate the feasibility of employing multiplexed force control of four pneumatic muscle actuators. In the system, pressure is controlled by a single proportional pressure valve. High-speed switching valves are used for activating the pressure control for each muscle actuator in the desired manner. Pneumatic cylinders are attached to the other ends of the muscles in order to cause controllable position disturbances. The displacement, force and pressure of each muscle are measured with appropriate sensors. The system behavior is investigated under position disturbances.

scholarly journals Hysteresis Modeling and Compensation of Fast Steering Mirrors with Hysteresis Operator Based Back Propagation Neural Networks

Micromachines ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 732
Author(s):  
Kairui Cao ◽  
Guanglu Hao ◽  
Qingfeng Liu ◽  
Liying Tan ◽  
Jing Ma
Keyword(s):  
Neural Network ◽  
Back Propagation ◽  
Hysteresis Model ◽  
Cooperative Movement ◽  
Hysteresis Operator ◽  
The Neural Network ◽  
Hysteresis Nonlinearity ◽  
Hysteresis Modeling ◽  
Hysteresis Characteristics ◽  
Inverse Hysteresis

Fast steering mirrors (FSMs), driven by piezoelectric ceramics, are usually used as actuators for high-precision beam control. A FSM generally contains four ceramics that are distributed in a crisscross pattern. The cooperative movement of the two ceramics along one radial direction generates the deflection of the FSM in the same orientation. Unlike the hysteresis nonlinearity of a single piezoelectric ceramic, which is symmetric or asymmetric, the FSM exhibits complex hysteresis characteristics. In this paper, a systematic way of modeling the hysteresis nonlinearity of FSMs is proposed using a Madelung’s rules based symmetric hysteresis operator with a cascaded neural network. The hysteresis operator provides a basic hysteresis motion for the FSM. The neural network modifies the basic hysteresis motion to accurately describe the hysteresis nonlinearity of FSMs. The wiping-out and congruency properties of the proposed method are also analyzed. Moreover, the inverse hysteresis model is constructed to reduce the hysteresis nonlinearity of FSMs. The effectiveness of the presented model is validated by experimental results.

Sign in / Sign up

Export Citation Format

Share Document