Robot Joint Torque Sensor Isolation via Magnetic Coupling
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Solution Overview
Problem
Existing joint driving apparatuses for robots face challenges in accurately detecting torque due to cross-axis disturbance forces and complexity, leading to reduced accuracy and increased size and weight, especially when dealing with large operation angles and complex cable routing.
Innovation Solution
A joint driving apparatus configuration where the torque sensor is installed between the driving unit and the housing unit, fixed to the first link, allowing for accurate torque detection without cross-axis interference, simplifying the mechanism, reducing weight, and eliminating the need for additional support structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the torque sensor rotates together with the measuring object, then the torque can be detected, but the sensor cable deforms along with motion of the drive shaft causing inaccurate detection and complicated cable routing
Solution Approach 1:
The patent divides the sensor system into two separate parts: the torque sensor remains stationary in the housing while the measuring object (drive shaft) rotates independently. This segmentation eliminates the need for rotating sensor cables, solving the cable routing complexity issue while maintaining torque detection capability through magnetic coupling between stationary and rotating components.
Solution Approach 2:
The patent introduces magnetic fields as an intermediary to transmit torque information from the rotating drive shaft to the stationary torque sensor. The magnetic coupling mechanism allows torque measurement without direct mechanical connection, eliminating cable deformation issues while maintaining accurate detection.
2Measurement precision
If the torque sensor is installed on the rotating side, then torque can be measured, but cross-axis disturbance forces reduce detection accuracy
Solution Approach 1:
The patent extracts the torque sensor from the rotating side and places it on the stationary housing side. By taking out the sensor from the rotating assembly, cross-axis disturbance forces that occur during rotation are eliminated from the measurement path, allowing accurate torque detection without interference from lateral forces.
Solution Approach 2:
Instead of placing the sensor on the rotating component as in conventional designs, the patent inverts the approach by placing the sensor on the stationary housing and measuring torque through the housing structure. This inversion removes the sensor from the path of cross-axis disturbance forces while maintaining measurement capability.
3Measurement precision
If additional support structures are added to isolate cross-axis forces, then torque detection accuracy improves, but the size and weight of the robot apparatus increases
Solution Approach 1:
The patent merges the torque sensor mounting function with the existing housing structure. The housing serves dual purposes: it provides mechanical support for the drive mechanism and simultaneously serves as the mounting structure for the torque sensor, isolating cross-axis forces without requiring additional support structures. This integration eliminates extra weight while maintaining detection accuracy.
Solution Approach 2:
The housing is designed to perform multiple functions: it provides structural support for the rotating components, houses the stationary torque sensor, and acts as a force isolation structure that protects the sensor from cross-axis disturbance forces. This multi-functionality eliminates the need for separate support structures, reducing overall weight.
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
This configuration enables high-accuracy joint torque control, reduces the size and weight of the robot apparatus, and enhances responsiveness and agility by isolating cross-axis forces from the torque sensor, thereby improving the reliability and durability of torque detection.
Implementation Method 1
an elastic body (521) made up of an inner ring portion (5212) and an outer ring portion (5211)
Implementation Method 2
relative displacement produced between the inner ring and outer ring when torque acts around a rotating shaft of a first member is detected as distortion of the elastic member of the torque sensor
Implementation Method 3
a bearing (54) adapted to rotatably support a drive shaft (51a)
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The present invention allows a joint driving apparatus (71-76) of a robot apparatus (1) to measure joint driving torque with high accuracy and perform joint torque control accurately and reliably using a simple, inexpensive, small, lightweight and sturdy configuration without being affected by cross-axis disturbance forces. A joint driving apparatus includes a housing unit (55) fixed to a first link (62); a bearing (54) mounted in the housing unit (55) and adapted to rotatably support a second link (63); a driving unit (80) housed in the housing unit (55) and adapted to rotationally drive the second link (63); a supporting unit (532, 56, 52) installed between the driving unit (80) and the housing unit (55) and adapted to support the driving unit (80) on the housing unit (55); and a torque sensor (52s) adapted to detect torque generated on the supporting unit (532, 56, 52) .