Industrial Robot Power Transmission Shaft Strain Detection
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Solution Overview
Problem
Conventional force sensors with distorting bodies are inadequate for high-force load applications in industrial robots, leading to vibration and reduced precision at high speeds, degrading the robots' performance in direct teaching scenarios.
Innovation Solution
An industrial robot configuration with a power transmission shaft of high rigidity, equipped with multiple strain gauges to detect minute strains, allowing for accurate external force identification and improved assist functionality while minimizing performance degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a force sensor with a distorting body is used to detect external forces, then the assist function during direct teaching is improved, but the rigidity of the robot body is reduced and end effector weight increases, degrading high-speed operation performance
Solution Approach 1:
The patent uses the power transmission shaft as an intermediary component to transmit external forces from the end effector to the drive unit. Instead of placing a force sensor directly at the end effector, the shaft acts as a mechanical intermediary that transmits forces to a location where strain gages can detect them, thereby providing assist functionality without compromising end effector rigidity or adding significant weight.
Solution Approach 2:
The patent replaces the conventional force sensor with a distorting body with a strain gage-based detection system on the power transmission shaft. This substitution uses strain measurement on a rigid shaft rather than mechanical deformation of a distorting body, maintaining rigidity while enabling force detection for assist functionality.
2Ease of operation
If a force sensor with a distorting body is used to detect external forces, then the assist function during direct teaching is improved, but the manufacturing precision and operating precision are reduced due to vibration
Solution Approach 1:
The power transmission shaft serves as a rigid intermediary that transmits external forces without the vibration and deformation issues associated with distorting bodies. By placing strain gages on this rigid shaft rather than using a distorting body, the system maintains manufacturing precision and operating precision while still enabling force detection for assist functionality.
3Ease of operation
If the rigidity of the robot body is reduced to facilitate force detection, then the assist function is improved, but the basic performance including carrying capacity and operating speed is degraded
Solution Approach 1:
The power transmission shaft acts as a mediator that enables force detection without requiring reduction of the robot body's rigidity. The shaft transmits external forces to the strain gage detection system while the main robot structure maintains its full rigidity and carrying capacity.
Solution Approach 2:
The patent applies local quality by making only the power transmission shaft strain-sensitive through attached gages, while the rest of the robot body maintains its full rigidity. This localized approach enables force detection without compromising the overall structural integrity and carrying capacity of the robot.
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
The configuration enhances the assist function during direct teaching, reduces the dead zone, and alleviates user satisfaction issues by accurately detecting external forces without significant rigidity loss or increased end effector weight, thus maintaining high-speed and high-precision operations.
Implementation Method 1
a plurality of strain gages (41, 42) installed on the power transmission shaft (55) and each configured to detect strain caused in the power transmission shaft (55)
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
In an industrial robot (15), a second arm configuring member (26) is located closely to an end effector (29) than a first arm configuring member (25) is. A drive unit (35D) is fixed to the first arm configuring member and configured to have an actuator (36D) and a speed reducer (37D) attached to the actuator. A power transmission shaft (55) is fixed to the speed reducer and the second arm configuration member such that the power transmission shaft composes part of a linkage member linking the first and second arm configuring members to each other and transmits power from the drive unit to the second arm configuring member. A plurality of strain gages (41, 42) are installed on the power transmission shaft, each gage detecting strain caused in the power transmission shaft. A determination unit (S102), which is in a controller (93), determines a magnitude and a direction of an external force exerted on the robot body, based on detection signals from the strain gauges. The controller drives and controls the drive unit based on the determined results.