Robot Gripper Force Control Using Current and Tactile Feedback
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Solution Overview
Problem
Existing robot grippers struggle to accurately control gripping force, especially in regions of small force, due to low detection precision and difficulty in achieving rapid force adjustments, leading to the need for different grippers for varying gripping force ranges.
Innovation Solution
A robot gripper system equipped with drive current detection, tactile sensors, and a control mechanism that computes and adjusts gripping force based on drive force and pressing force, using error minimization to achieve precise control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current detection resolution is increased to improve gripping force detection precision, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent introduces a reaction force detection mechanism as an intermediary element. Instead of directly measuring the drive current with high precision, the system detects the reaction force generated by the motor through a mechanical sensor, which provides sufficient measurement precision without requiring high-resolution current detection hardware, thus resolving the contradiction between measurement precision and device complexity
Solution Approach 2:
The patent replaces electrical measurement (current detection) with mechanical measurement (reaction force detection). By using a mechanical sensor to detect the reaction force generated by the motor, the system achieves accurate gripping force measurement without relying on high-resolution electrical current detection, thereby reducing device complexity while maintaining measurement precision
2Speed
If control cycle is shortened to improve response speed, then speed improves, but measurement precision deteriorates
Solution Approach 1:
The patent implements a feedback control mechanism where the detected reaction force is continuously fed back to adjust the motor output. This feedback loop enables the system to achieve rapid gripping force adjustments by using the mechanical reaction force signal, which has sufficient update rate, to continuously correct the drive current, thereby achieving both fast response speed and adequate measurement precision
Solution Approach 2:
The system utilizes the motor's own reaction force as the measurement signal. The motor naturally generates a reaction force proportional to its output torque, and by detecting this inherent reaction force, the system achieves both rapid response (since the reaction force immediately reflects motor output changes) and sufficient measurement precision without requiring external measurement infrastructure
3Adaptability or versatility
If a single gripper is used for multiple gripping force ranges, then adaptability improves, but manufacturing precision requirements increase
Solution Approach 1:
The patent implements dynamic gripping force control by continuously adjusting the motor drive current based on the detected reaction force. This dynamic adjustment capability allows a single gripper to adapt to multiple gripping force ranges (from weak to strong forces) while maintaining precise control throughout the entire range, eliminating the need for different grippers for different force requirements
Data Source
AI summary
This robot comprises: a finger that grips a workpiece; a motor that drives the finger; a driving current detection unit that detects a driving current of the motor; a gripper including a tactile sensor provided in the finger; a driving force calculation unit that calculates a driving force applied to the workpiece by the finger on the basis of a driving current value of the motor; a pressing force calculation unit that calculates a pressing force that the tactile sensor receives from the workpiece on the basis of a detection value of the tactile sensor; and a control unit that determines which of the driving force and the pressing force is to be used on the basis of a gripping force setting value that is a setting value of the gripping force applied to the workpiece by the finger and controls the gripping force using the value of the driving force or the pressing force which is determined to be used.