Robot Arm Torque Control via Gravity Compensation
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Solution Overview
Problem
Existing robot arm control systems face difficulties in performing position and force control due to the complexity of adjusting torque values and maintaining safety, particularly when using electromagnetic clutches, which require additional structures and complex computations to account for the robot's weight and posture.
Innovation Solution
A robot arm control system that combines a torque adjustment device and a gravity-compensating mechanism to simplify computational processing, allowing for position and force control through motor adjustment and torque manipulation, while detecting external forces and weights using intentional slippage and encoder feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an electromagnetic clutch is used to adjust torque values according to operation mode, then torque adjustability is improved, but device complexity and computational requirements increase due to the need for additional safety structures and complex moment calculations
Solution Approach 1:
The patent extracts the gravity compensation function into a separate mechanism (spring or counterweight) that operates independently from the electromagnetic clutch. This separation allows the clutch to focus solely on torque adjustment for position and force control without needing to calculate and compensate for gravity effects, thereby reducing computational complexity and simplifying the control system while maintaining torque adaptability.
2Reliability
If a spring is used as a compliance function to mitigate collision impact, then safety is improved, but position control difficulty increases due to the need to adjust spring elasticity during operation
Solution Approach 1:
The patent employs the electromagnetic clutch to dynamically adjust the stiffness characteristics of the robot arm during operation. By varying the clutch engagement torque, the system can transition between compliant states (for safety during potential collisions) and rigid states (for precise position control), effectively decoupling the trade-off between safety and controllability that exists with fixed-spring systems.
3Reliability
If an elastic element such as a spring is attached to the robot arm for collision mitigation, then safety is improved, but acceleration speed decreases and vibration may occur
Solution Approach 1:
The electromagnetic clutch enables dynamic stiffness adjustment that allows the robot arm to operate in a rigid, high-acceleration mode during normal operation, and only becomes compliant when collision is detected or anticipated. This on-demand compliance eliminates the continuous acceleration limitations and vibration issues associated with permanently attached springs while maintaining collision safety.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables simple and effective position and force control of the robot arm with reduced complexity, allowing for safer operation by mitigating impacts and detecting external forces without complex calculations, and enabling smaller torque limit values due to gravity compensation.
Implementation Method 1
a gravity-compensating mechanism for cancelling an effect of gravity of the robot arm
Implementation Method 2
by allowing intentional slippage of a connection state of the motor and the robot arm by the torque adjustment device
Data Source
Figure 1
Figure 2
AI summary
A control system (10) according to the present invention includes a robot arm (11) provided in a manner capable of moving in a given space, a motor (14) for operating the robot arm (11), a torque adjustment device (16) for operating in a manner capable of adjusting a transmitted torque that is transmitted from the motor (14) to the robot arm (11), and a control device (19) for performing operation control of the robot arm (11). The robot arm (11) is provided with a gravity-compensating mechanism (12) for cancelling an effect of gravity due to the robot arm (11), and the control device (19) commands adjustment of the transmitted torque at the torque adjustment device (16), without taking into account the effect of the gravity of the robot arm (11).