A Robot Compliant Joint Design With Adjustable Viscous Damping

Variable damping compliant joints can improve the dynamic performance of traditional compliant joints and reduce the problem of oscillation overshoot caused by the introduction of elastic components into compliant joints.In recent years,it has become the frontier and hot spot of robot theory and technology research,but there are few studies in our country.In order to balance the safety and dynamic performance of robot joints,it is important to study the variable daping compliant joints.In this paper,a robotic damping adjustable flexible joint is designed,which is mainly studied from the following aspects.(1)The variable damping joint is freed from the mechanism by which the compliant joint changes its flexibility by changing the stiffness.It uses a method of changing the viscous damping to change the compliance.A robot damping adjustable joint is designed.It uses a unique variable damping principle to change the damping by changing the size of the orifice.According to the proposed design principles and indicators,the crank slider,slip ring and orifice are skillfully utilized.A mechanism such as a rotating piston completes the overall design of the joint.(2)A mathematical model of joint damping force was established.The variation characteristics and range of damping torque and damping coefficient are derived.The dynamics model of the joint was established,and the dynamic model was simulated by MATLAB/Simulink to explore the influence of different damping coefficients on the dynamic performance of the joint.The results show that when the damping coefficient is small,there will be a large vibration.When the damping coefficient is large,although there is no vibration,the rise time is longer.Finally,when the damping coefficient takes a reasonable value,the vibration is suppressed and can be stabilized quickly.(3)The force analysis and static check of the key parts ensure that the parts can operate normally without damage.Considering that if the excitation frequency of the motor is close to the natural frequency of the working device,it is easy to cause vibration damage of the parts caused by resonance.Therefore,the ANSYS software is used to perform modal analysis on key parts,which will provide reference for future structural optimization Considering that the load provided by the main motor to the working device in actual work is arbitrarily changed with time.Therefore,ANSYS was used to analyze the transient dynamics of key parts of the joint.The strength of key parts is guaranteed.(4)Test the variable damping joint.An experimental platform for the prototype was built.A joint control strategy is established.The main motor motion adopts PID position control.The variable damping module calculates the rotation angle of the variable damping motor based on the relative speed of the input shaft output.Thereby generating a set damping coefficient.The variable damping compliant joint sets different damping values and collects data with the sensor.A step position tracking experiment was performed.Observing the dynamic characteristics of the joint output,the variable damping joint can basically achieve the purpose of reducing system vibration.