Development of a Virtual Force Sensor for a Low-Cost Collaborative Robot and Applications to Safety Control

Area of Science:

• Robotics
• Control Systems
• Mechanical Engineering

Background:

• Collaborative robot arms often use flexible mechanisms and force sensors for safety, increasing costs.
• High production costs limit the use of current safety-enhanced robot arms in low-cost service applications.

Purpose of the Study:

• To propose a low-cost, sensorless rigid robot arm design.
• To enable safety collision detection and low-precision force control without expensive sensors.

Main Methods:

• A virtual force sensor estimates external torques using motor electric current and system model errors.
• A contact force observer estimates external contact forces on the robot arm's end-effector.
• A torque saturation limiter adjusts joint torque for real-time stiffness regulation and impedance control.

Main Results:

• The proposed design achieves sensorless collision detection and force control.
• It enables real-time stiffness regulation and impedance control through model-based control.
• The approach offers a cost-effective alternative to conventional multisensor flexible designs.

Conclusions:

• The sensorless rigid robot arm design successfully enhances safety and force control capabilities.
• This innovation reduces production costs, making collaborative robots more accessible for low-cost service applications.