Robot Arm Collision Stopping Method
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Solution Overview
Problem
Existing robot systems face mechanical damage and trajectory deviations when colliding with obstacles due to inadequate control methods, leading to potential secondary collisions and damage, especially when high-speed servo motors with large inertia are involved.
Innovation Solution
A method for selectively stopping a robot arm's movement around the wrist and fundamental axes based on collision detection, motor rotational direction, and speed, using pullback and flexible stopping processes to minimize damage and ensure return to the commanded trajectory.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the robot switches to flexible control mode upon collision detection, then the collision torque is reduced, but the robot may go out of control and suffer mechanical damage when operating at high speed with large inertia
Solution Approach 1:
The control mode is dynamically changed based on collision detection results. When collision is detected, the system switches from rigid control mode to flexible control mode, adjusting the control parameters to accommodate the collision force while maintaining stability. This parameter change allows the robot to adapt its stiffness characteristics in response to external forces.
Solution Approach 2:
The robot control system transitions from a static control mode to a dynamic one where the control characteristics can change in real-time. The flexible control mode enables the robot to dynamically adjust its response to collision forces, allowing controlled movement during collision rather than rigid resistance, thereby reducing peak forces while maintaining operational control.
2Force
If the robot operates in flexible control mode after collision, then the collision force is accommodated, but the robot deviates from the commanded trajectory and may cause another collision
Solution Approach 1:
The system continuously monitors the robot's position and compares it with the commanded trajectory. When flexible control mode is activated due to collision, the feedback mechanism detects the trajectory deviation and provides correction signals to guide the robot back to the intended path, ensuring that the robot returns to the correct trajectory after accommodating the collision force.
Solution Approach 2:
The system prepares for trajectory correction by storing the commanded trajectory information before collision occurs. This preliminary preparation allows the control system to quickly calculate and execute the necessary corrections to return the robot to its intended path after the collision, minimizing the time spent off-trajectory and reducing the risk of secondary collisions.
3Force
If the servo motor is locked to produce large torque during collision, then the robot can resist the obstacle force, but mechanical damage to the robot and obstacle may result
Solution Approach 1:
The system converts the potentially harmful rigid locking response into a beneficial flexible response. By switching to flexible control mode upon collision detection, the robot transforms what would be a damaging rigid impact into a controlled, compliant interaction that reduces peak forces on both the robot and the obstacle while maintaining operational control.
Solution Approach 2:
The control system prepares for collision by having the flexible control mode ready to activate. This preliminary preparation acts as a control-level cushioning mechanism, where the system is pre-configured to switch from rigid to compliant behavior upon detecting collision, thereby cushioning the impact before it can cause mechanical damage.
Data Source
AI summary
A robot system includes a robot arm driven by a motor, a collision detector that detects a collision between the robot arm and an obstacle, which is provided on the robot arm, and a stopping method selector that controls the robot arm by selecting any one of all stopping methods on the basis of the information obtained by the collision detector, thereby selecting a stopping method in accordance with the status of the collision.