An improved force-based impedance control method for the HDU of legged robots

Area of Science:

• Robotics
• Control Systems Engineering
• Mechanical Engineering

Background:

• Hydraulic drive units (HDUs) offer advantages like high power-to-weight ratios for legged robots.
• Legged robot control is complex due to environmental variations and inherent hydraulic system nonlinearities.
• Existing impedance control methods struggle with accuracy in dynamic, real-world scenarios.

Purpose of the Study:

• To improve the control accuracy of hydraulic drive units (HDUs) in legged robots.
• To address the limitations of traditional impedance control in dynamic and nonlinear hydraulic systems.
• To enhance the performance of legged robots navigating complex environments.

Main Methods:

• An improved second-order dynamic compliance control system is proposed for HDUs.
• The system incorporates a compliance-enhanced controller and a feedforward compensation controller for the inner force control loop.
• The dynamic compliance composition of inner and outer control loops is rearranged.

Main Results:

• The proposed control system significantly enhances impedance control accuracy.
• Experimental results demonstrate superior performance compared to traditional force-based impedance control.
• The method effectively mitigates issues related to nonlinearity and time-varying parameters in hydraulic systems.

Conclusions:

• The improved impedance control system offers a robust solution for legged robot control.
• This advancement is crucial for reliable robot navigation and interaction with dynamic environments.
• The findings pave the way for more sophisticated and accurate legged robot applications.