Robot Arm Collision Detection Using Residual Torque Balance
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Solution Overview
Problem
In surgical robot systems, collisions between robot arms are difficult to detect and prevent when the robots are not mounted on a common chassis, as the relative positions of the robots are not inherently known, making it challenging to use existing collision detection mechanisms.
Innovation Solution
A robotic system with position and torque sensors on each arm, a control unit that determines gravitational torques and residual torques, and calculates candidate forces to detect collisions without knowing the relative positions of the robots, allowing it to control the arms to prevent or move away from collisions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If robots are independently mounted without a common chassis, then system adaptability and flexibility are improved, but collision detection capability deteriorates due to unknown relative positions
Solution Approach 1:
The patent replaces the traditional mechanical/optical sensing system (which requires known relative positions and sensors mounted on robots) with a force-based detection system using torque sensors at the base. By measuring reaction forces and torques generated during collisions, the system can detect collisions without needing to know robot positions or have sensors on the robots themselves, thus resolving the contradiction between mounting flexibility and collision detection capability
Solution Approach 2:
The patent introduces the base platform and torque sensors as an intermediary element between the robots and the collision detection system. Instead of directly sensing robot positions or using complex sensor arrays on robots, the system uses the base as a mediator to detect collisions through force measurements, enabling collision detection while maintaining independent robot mounting flexibility
2Device complexity
If relative positions of robots are not determined, then system complexity is reduced, but collision prevention capability deteriorates
Solution Approach 1:
The patent eliminates the need for complex position determination systems (sensors, cameras, tracking systems) by substituting them with a force-based detection method using torque sensors at the base. This reduces device complexity while maintaining reliable collision prevention by detecting collisions through force measurements rather than position monitoring
Solution Approach 2:
The base platform serves itself by using its own torque sensors to detect collisions caused by robot interactions. The system doesn't require external positioning systems or inter-robot communication; the base automatically detects collisions through the forces generated when robots collide, simplifying the overall system while ensuring reliable collision prevention
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
Effectively detects and prevents collisions between robot arms in a surgical robotic system, even when not mounted on a common chassis, ensuring safe operation by determining candidate forces that balance opposing forces on each arm.
Implementation Method 1
a position sensor and torque sensor configured to sense the joint
Implementation Method 2
a position sensor and torque sensor configured to sense the joint
Data Source
AI summary
A robotic system comprises two robots and a control unit. Each robot has a base and an arm extending from the base to an attachment for an instrument. Each arm comprises a plurality of joints whereby the configuration of the arm can be altered. Each robot comprises a driver for each joint configured to drive the joint to move, and position and torque sensors. The control unit controls the drivers in dependence on inputs from the sensors. The control unit: determines the gravitational torques on the joints of the arms of the robots in the arm configurations indicated from the inputs from the position sensors; from the inputs from the torque sensors and the determined gravitational torques, determines residual torques on the joints of the arms of the robots in the indicated arm configurations; calculate a candidate force for each arm which when applied to that arm would cause the determined residual torques; and determines a collision if a candidate force on the arm of the first robot balances an opposing candidate force on the arm of the second robot.