Actuation Spaces Synthesis of Lower-Mobility Parallel Mechanisms Based on Screw Theory

et al. 2022

Micromachines

The ankle is a crucial joint that supports the human body weight. An ankle sprain will adversely affect the patient’s daily life, so it is of great significance to ensure its strength. To help patients with ankle dysfunction to carry out effective rehabilitation training, the bone structure and motion mechanism of the ankle were analyzed in this paper. Referring to the configuration of the lower-mobility parallel mechanism, a 3-RRS (R and S denote revolute and spherical joint respectively) parallel ankle rehabilitation robot (PARR) was proposed. The robot can realize both single and compound ankle rehabilitation training. The structure of the robot was introduced, and the kinematics model was established. The freedom of movement of the robot was analyzed using the screw theory, and the robot kinematics were analyzed using spherical analytics theory. A circular composite rehabilitation trajectory was planned, and the accuracy of the kinematics model was verified by virtual prototype simulation. The Multibody simulation results show that the trajectory of the target point is basically the same as the expected trajectory. The maximum trajectory error is about 2.5 mm in the simulation process, which is within the controllable range. The experimental results of the virtual prototype simulation show that the maximum angular deflection error of the three motors is 2° when running a circular trajectory, which meets the experimental requirements. Finally, a control strategy for passive rehabilitation training was designed, and the effectiveness of this control strategy was verified by a prototype experiment.

Section: Mechanical Structure Of the 3-rrs Parrmentioning

confidence: 99%

Design and Experimental Research of 3-RRS Parallel Ankle Rehabilitation Robot

Zou

et al. 2022

Micromachines

“…However, owing to the lack of comprehensive analyses, the algorithm lacked generality in multiple situations, even though satisfactory results were obtained in the specific experiments. Among such strategies, adaptive sliding mode control is a valuable control method [13,14].…”

Section: Introductionmentioning

confidence: 99%

Parameter Adaptive Sliding Mode Trajectory Tracking Strategy with Initial Value Identification for the Swing in a Hydraulic Construction Robot

Hou

Zhao

2022

Preprint

A novel trajectory tracking strategy is developed for a double actuated swing in a hydraulic construction robot. Specifically, a nonlinear hydraulic dynamics model of a double actuated swing is established, and a robust adaptive control strategy is designed to enhance the trajectory tracking performance. When an object is grabbed and unloaded, the inertia of a swing considerably changes, and the performance of the estimation algorithm is generally inadequate. Thus, it is necessary to establish an algorithm to identify the initial value of the moment of inertia of the object. To this end, this paper proposes a novel initial value identification algorithm based on a two-DOF robot gravity force identification method combined with computer vision information. The performance of the identification algorithm is enhanced. Simulations and experiments are performed to verify the effect of the novel control scheme.

“…The fuzzy logic in the algorithm reduces the complexity of mathematical modeling which is commonly a complex and time-consuming process, but the lack of comprehensive analysis leads to the problem of generality on multi situations, even good results have been obtained in the specified experiments. Among the methods, adaptive sliding mode control is a very important one [13,14].…”

Section: Introductionmentioning

confidence: 99%

Parameter Adaptive Sliding Mode Trajectory Tracking Strategy With Initial Value Identification For Swing In A Hydraulic Construction Robot

Hou

Zhao

2021

Preprint

A novel trajectory tracking strategy is developed for the swing DOF with double actuated cylinder in a hydraulic construct robot. When the work object is grabbed and unload, the inertia parameter of swing varies greatly and the estimation algorithm is commonly insufficient. Aiming at this feature, a novel nonlinear hydraulic dynamics model is established for the double actuated hydraulic cylinder in the system and a robust adaptive control strategy with parameter adaptive estimation is designed to improve the trajectory tracking performance. Aiming at the problem of insufficient convergence speed of the identification algorithm, a method of robotic gravity identification combined with stereo vision information is proposed to obtain the mass and moment of inertia parameters of the working object so that the initial value is close to the real value. Simulations and experiments are presented to validate the effect of the novel strategy.