Robot Arm Sensor Unit with Soft Member and Protrusions for Contact Detection
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Solution Overview
Problem
Conventional industrial robots face inaccuracies and reduced responsiveness in contact detection due to a single threshold value for torque detection, leading to inefficient production and potential harm when interacting with humans, as the distance from the contact point to the joint affects detection accuracy and increases unnecessary protective stops.
Innovation Solution
A sensor unit with a soft member and sensor sheet that covers a predetermined portion of the robot arm, featuring protrusions to concentrate force and a support system creating a gap, allowing for sensitive contact detection by exceeding a threshold pressure before significant contact force is applied, thus reducing the force on humans and improving detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single threshold value is used for torque detection, then the detection system is simple, but detection accuracy and responsiveness vary depending on contact position
Solution Approach 1:
The arm surface is divided into multiple detection regions, each equipped with its own sensor unit. Each sensor unit independently monitors torque in its specific region, allowing for position-specific detection thresholds and improving overall detection accuracy without requiring a single complex thresholding system.
Solution Approach 2:
Different detection thresholds and sensitivity levels are applied to different regions of the arm based on their specific operational characteristics and risk profiles. This allows each region to have optimized detection parameters tailored to its local requirements, improving measurement precision while maintaining system manageability.
2Measurement precision
If the threshold is lowered to detect contact closer to the joint, then detection sensitivity improves, but unnecessary protective stops increase
Solution Approach 1:
The arm is divided into multiple detection zones with different threshold settings. Regions closer to the joint can use lower thresholds for high sensitivity, while other regions use higher thresholds to reduce false positives. This segmentation allows simultaneous optimization of sensitivity and productivity across different arm regions.
Solution Approach 2:
Each detection region has locally optimized threshold values based on its specific operational context, risk level, and operational requirements. This allows high sensitivity where needed without triggering unnecessary stops in other regions, thereby maintaining production efficiency.
3Productivity
If the operating speed of the industrial robot is increased, then productivity improves, but contact force to humans may exceed acceptable values
Solution Approach 1:
Sensor units are positioned on the arm surface to detect contact before significant force is transmitted to humans. The system performs preliminary detection at multiple points, allowing the control system to initiate deceleration before contact force reaches harmful levels, thus enabling higher operating speeds while maintaining safety.
Solution Approach 2:
The sensor units continuously monitor contact conditions and provide real-time feedback to the control system. This feedback mechanism allows dynamic adjustment of operating parameters, enabling the robot to maintain high speeds during normal operation while automatically decelerating when contact is detected, thus balancing productivity and safety.
4Object-affected harmful factors
If a sensor unit with soft member is used to reduce contact force, then safety improves, but device complexity increases
Solution Approach 1:
A soft member is introduced as an intermediary between the hard arm surface and the human body. This soft member deforms under contact force, reducing the peak force transmitted to humans while the embedded sensor detects the contact condition. This intermediary approach improves safety without requiring complete redesign of the arm structure.
Solution Approach 2:
The sensor unit incorporates a soft, flexible member that covers the arm surface. This flexible layer conforms to contact conditions, distributes force, and protects against injury while containing the sensing elements. The use of flexible materials simplifies the overall structure compared to rigid alternative designs.
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 sensor unit effectively reduces contact force and enhances detection sensitivity, enabling the robot to decelerate promptly when contact force approaches acceptable limits, thereby increasing operating speed without unnecessary stops and ensuring safer human-robot interactions.
Implementation Method 1
a sensor sheet, which is formed into a sheet, having a detection member arranged to be opposed to the inner surface of the soft member to detect pressure applied thereto
Implementation Method 2
the soft member can deform and absorb the impact
Implementation Method 3
the soft member can deform and absorb the impact
Implementation Method 4
a plurality of protrusions protruding from the inner surface of the soft member towards the detection member
Data Source
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AI summary
A senor unit (50) preferably applied to an industrial robot (10) is provided for detecting contact with objects with higher sensitivity and also reducing a contact force caused when being contacted with objects. In the sensor unit (50), a soft member (53) has an inner surface (53a) and is made of a material which is lower in hardness (softer) than a surface of the arm (22) and formed in a shape that covers a surface of a predetermined portion (41c) of the arm (22). A sensor sheet (57) has detection members (57a) arranged to be opposed to the inner surface (53a) of the soft member (53) to detect pressure applied thereto, and detects contact when the detected pressure exceeds a threshold value. A plurality of protrusions (54) protrude from the inner surface (53a) of the soft member (53) towards the detection members (57a). A support (54A, 58, 57b; 154A, 58, 57b; 56, 58, 57b; 59, 57b; 159; 254A, 58, 57b) supports the soft member (53) such that a predetermined-size gap (G) is formed between the detection members (57a) and the protrusions (54).