Variable Rigidity Actuator for Robot Joint Control
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Solution Overview
Problem
Existing actuating apparatuses for robot joints cannot determine and maintain the required level of rigidity at specific task positions, such as the hand tip position, leading to inefficiencies in joint control and vibration suppression.
Innovation Solution
An actuating apparatus with a controller that calculates and adjusts rigidity threshold values for joints using a coefficient matrix based on rotational angles, incorporating variable rigidity elements and viscosity coefficients, and a system to change these properties dynamically to match the required rigidity and suppress vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a flexible passive joint with variable rigidity is used, then the robot arm can adapt to different task requirements, but the system cannot determine the appropriate rigidity level for specific task positions
Solution Approach 1:
The system dynamically adjusts the rigidity parameter of the flexible transmitting assembly based on calculated threshold values. The controller modifies the rigidity parameter in real-time according to the robot's current state and task requirements, enabling adaptation to different tasks while maintaining precise control over rigidity levels at specific task positions
Solution Approach 2:
The system employs feedback through the rigidity threshold value calculator, which continuously monitors the robot arm's state including joint angles and task position, then feeds back appropriate rigidity threshold values to the controller. This closed-loop feedback mechanism enables the system to automatically determine and maintain appropriate rigidity levels without manual intervention
2Manufacturing precision
If rigidity is increased at joints to maintain required rigidity at task position, then control precision improves, but vibrations in the joints increase
Solution Approach 1:
The system dynamically adjusts the rigidity parameter based on calculated threshold values rather than maintaining constant high rigidity. By changing rigidity parameters adaptively according to task requirements and current state, the system achieves precise control when needed while reducing rigidity (and thus vibrations) when high rigidity is not required
Solution Approach 2:
The flexible transmitting assembly enables dynamic adjustment of rigidity characteristics in real-time. This dynamic capability allows the system to optimize the balance between control precision and vibration suppression by adjusting rigidity levels according to the operational context, rather than being fixed at a constant high rigidity state
3Ease of operation
If variable rigidity elements are incorporated into the flexible transmitting assembly, then the system can control joint rigidity, but the device complexity increases
Solution Approach 1:
The system controls joint rigidity by changing physical parameters of the flexible transmitting assembly (such as pre-tension force or geometric configuration) rather than adding complex mechanical switching mechanisms. This parameter-based control approach maintains ease of operation while managing device complexity through software-controlled parameter adjustment
Solution Approach 2:
The variable rigidity element serves multiple functions: it provides both the flexible transmission necessary for the robot's operation and the adjustable rigidity control needed for precise task execution. This multi-functionality reduces overall device complexity by combining what could be separate components into a single integrated element
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 apparatus effectively determines and maintains the required rigidity at task positions, ensuring precise control and suppressing vibrations in robot joints.
Implementation Method 1
a flexible transmitting assembly which includes a variable rigidity element a rigidity of which is variable in directions of rotation of the joints
Implementation Method 2
a variable viscosity coefficient element for varying a viscosity coefficient in directions of rotation of the joints
Implementation Method 3
an inertia matrix of the actuator, which is determined based on the rotational angles of the rotary prime movers
Data Source
AI summary
An actuating apparatus includes an actuator including flexible transmitting assemblies disposed between a plurality of joints, and a plurality of motors for actuating the joints. Each of the motors includes a variable rigidity element, the rigidity of which is variable in directions of rotation of the joints, and a controller for controlling the actuator. The controller includes a rigidity threshold value calculator for calculating rigidity threshold values of the joints, based on a required rigidity for a predetermined task position on a link and a coefficient matrix determined based on rotational angles of the motors.