Spring-Compensated Robotic Joints for Dynamic Payload Gravity Balance
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Solution Overview
Problem
Conventional robotic manipulators face challenges in dynamically adjusting gravity compensating torque when payloads change, leading to increased actuator efforts and reduced safety and robustness due to the reliance on passive gravity-balancing mechanisms and highly geared electric motors, which increase apparent inertia.
Innovation Solution
The implementation of a robotic manipulator with a plurality of spring compensated joints, each comprising a four-bar linkage mechanism, gravity compensating springs, a spring adjustment mechanism, and an inertial actuator, allowing for active actuation and feedback control to dynamically adjust the lifting force and gravity compensating torque in real-time, reducing the need for high actuator efforts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If highly geared electric motors are used to compensate for gravity torque, then the required actuator torque is reduced, but the apparent inertia increases, reducing safety and robustness
Solution Approach 1:
The gravity compensation function is segmented from the actuator system and implemented through a dedicated passive spring mechanism at each joint. This separates the gravity compensation task from the actuator, allowing the actuator to focus on dynamic control while the spring handles static gravity torque, thereby reducing required actuator torque without increasing apparent inertia.
Solution Approach 2:
Passive springs are installed at each joint to provide counterbalancing torque that opposes the gravity torque. These springs act as mechanical counterweights that automatically compensate for the weight of the manipulator links, reducing the torque demand on actuators while maintaining system dynamics characteristics.
2Force
If passive gravity-balancing springs are used, then actuator torque requirements are reduced, but the system cannot dynamically adjust when payload changes
Solution Approach 1:
The spring pre-load forces are made dynamically adjustable through actuators that can modify the spring compression or extension. This allows the gravity compensation torque to be dynamically altered in real-time based on payload changes, combining the benefits of passive spring compensation with active adaptability.
Solution Approach 2:
The system incorporates sensors to detect payload mass and joint positions, and uses feedback control to dynamically adjust the spring pre-load forces. This closed-loop control enables the gravity compensation mechanism to adapt to varying payloads while maintaining optimal actuator torque requirements.
3Ease of operation
If springs are used to counterbalance gravity, then the manipulator behaves as if in gravity-less environment, but the springs are passive elements that cannot dynamically alter compensating torque
Solution Approach 1:
The springs provide automatic gravity compensation that makes the manipulator behave as if in a gravity-less environment during normal operation. The passive spring mechanism self-adjusts to maintain balance without requiring active control intervention, while the ability to dynamically modify pre-load forces provides adaptability when needed.
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 solution enables the robotic manipulator to maintain gravity balance with dynamically varying payloads, reducing actuator efforts and enhancing safety and robustness by actively adjusting the lifting force and compensating torque, thereby improving its ability to handle changing payloads and external disturbances.
Implementation Method 1
at least one gravity compensating spring coupled between links of the four-bar linkage mechanism
Implementation Method 2
The at least one gravity compensating spring may include two gravity compensating springs
Implementation Method 3
a four-bar linkage mechanism, at least one gravity compensating spring coupled between links of the four-bar linkage mechanism
Implementation Method 4
an inertial actuator coupled between links of the four-bar linkage mechanism to effectuate rotational movement of the four-bar linkage mechanism and to apply an adjustable amount of force to accelerate and manipulate a payload
Data Source
AI summary
A robotic manipulator comprises a plurality of spring compensated joints, each including a four-bar linkage mechanism, a gravity compensating spring, a spring adjustment mechanism, a spring adjustment actuator and an inertial actuator. The gravity compensating spring is coupled between two links of the four-bar linkage mechanism at two different spring attachment points to provide a lifting force opposing a gravitational load force. The spring adjustment mechanism is coupled to alter a position of one of the spring attachment points. The spring adjustment actuator is coupled to move the spring adjustment mechanism to alter the position of the spring attachment point and adjust the amount of lifting force provided by the spring. The inertial actuator is coupled between links of the four-bar linkage mechanism to effectuate rotational movement of the four-bar linkage mechanism and apply an adjustable amount of force to accelerate and manipulate a payload handled by the robotic manipulator.