Robot Wrist Torque Estimation for 3D Contact Detection
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Solution Overview
Problem
Conventional robots lack effective detection of contact between operators and tools, particularly in three-dimensional spaces, and are costly due to the need for torque sensors across all joints, which also complicates safe operation.
Innovation Solution
A robot system with torque sensors only on basic joints, using motor current detection to estimate torque on wrist joints, allowing for sensitive contact detection and reduced costs by eliminating torque sensors on wrist joints, while ensuring operator safety through controlled motor operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If torque sensors are installed on all joints (basic joints and wrist joints), then contact detection precision is improved, but device cost and complexity increase
Solution Approach 1:
The patent extracts torque sensors only from the wrist unit, removing them from basic joints. This selective extraction maintains contact detection capability through sensors on wrist joints while reducing overall device complexity and cost by eliminating redundant sensors on basic joints.
Solution Approach 2:
The patent uses motor current detection as a substitute (copy) for torque sensor measurement on basic joints. By detecting motor current and calculating torque from it, the system achieves torque measurement functionality without physically installing torque sensors on all joints, thereby reducing device complexity.
2Measurement precision
If torque sensors are installed on all joints, then operator contact detection is improved, but manufacturing cost increases
Solution Approach 1:
The patent extracts torque sensors only from the wrist unit, removing them from basic joints. This selective extraction maintains operator contact detection capability through sensors on wrist joints while reducing manufacturing cost by eliminating expensive torque sensors from basic joints.
Solution Approach 2:
The patent uses motor current detection as a cheaper alternative to torque sensors for basic joints. Motor current is an inexpensive parameter to measure compared to torque sensors, providing a cost-effective solution for torque estimation on basic joints while maintaining manufacturing economy.
3Manufacturing precision
If torque sensors are installed on wrist joints, then posture control of attached tools is improved, but device cost increases
Solution Approach 1:
The patent applies torque sensors locally only to the wrist unit where they are most needed for posture control. This localized application maintains precise posture control of attached tools while avoiding the unnecessary complexity and cost of installing torque sensors on all joints, including basic joints.
Solution Approach 2:
The patent segments the robot into basic joints and wrist unit, applying torque sensors only to the wrist unit segment. This segmentation allows posture control precision to be maintained where critical (wrist) while reducing overall device complexity by not instrumenting the entire robot system with torque sensors.
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 sensitive detection of operator contact and cost reduction by eliminating expensive torque sensors on wrist joints, ensuring safety and efficient operation in three-dimensional spaces without compromising posture control of attached tools.
Implementation Method 1
Only the basic joints are provided with torque sensors configured to detect torque of the basic joints about axis lines
Implementation Method 2
a high drive power servomotor for driving each of a first shaft to a third shaft, and a low drive power servomotor for driving each of a fourth shaft to a sixth shaft
Data Source
AI summary
A robot includes: a wrist unit including a plurality of wrist joints; and a plurality of basic joints configured to determine the position of the wrist unit in a three-dimensional space. Only the basic joints are provided with torque sensors configured to detect torque of the basic joints about axis lines.