Variable Admittance Control for Overhead Crane Inertia Reduction
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Solution Overview
Problem
Overhead bridge cranes with manual or partially motorized systems face challenges in smooth motion due to significant inertia from balancing devices, which can hinder operator efficiency and stability, especially during horizontal movements.
Innovation Solution
A robotic system with a sensing handle and controller infers the operator's intentions by measuring force to adjust admittance parameters, allowing for variable virtual mass and damping to simulate reduced inertia, enhancing ergonomics and stability during motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If balancing devices (counterweights or pressurized air systems) are used to compensate for payload weight, then the operator's task is eased, but significant inertia is added to the system which hinders smooth horizontal motion and operator efficiency
Solution Approach 1:
The patent replaces traditional mechanical balancing systems (counterweights or pressurized air cylinders) with a control system that uses force sensing and variable admittance control. The sensing handle measures operator force, and the controller dynamically adjusts virtual mass parameters to provide assistance without adding physical mass, thereby eliminating the inertia problem while maintaining ease of operation.
Solution Approach 2:
The system dynamically changes the admittance parameters (virtual mass and damping) based on the operator's inferred intentions and system state. By varying these control parameters in real-time, the system provides adaptive assistance that eases operation without the fixed inertia penalty of physical balancing devices.
2Productivity
If high horizontal traveling speed is achieved, then productivity is improved, but the inertia from balancing systems becomes a major drawback causing rough and bouncy motion
Solution Approach 1:
The system dynamically adjusts the virtual mass and damping parameters based on the operator's inferred intentions (acceleration, deceleration, velocity). This dynamic adaptation allows smooth motion at high speeds by reducing virtual mass during acceleration phases and increasing damping during deceleration, eliminating the bouncy behavior caused by fixed-mass balancing systems.
Solution Approach 2:
The system continuously monitors operator force through the sensing handle and uses this feedback to infer intentions and adjust admittance parameters in real-time. This closed-loop control ensures smooth motion at high speeds by continuously adapting the virtual inertia to match the operator's needs and system state.
3Speed
If fully motorized actuators are used to support payload weight, then vertical motion capability is improved, but powerful actuators are required adding device complexity and power consumption
Solution Approach 1:
The system uses the operator's own force input as the primary actuation source. The sensing handle captures the operator's natural pushing and pulling forces, and the variable admittance control amplifies and directs these forces to achieve both vertical and horizontal motion, eliminating the need for separate powerful motorized actuators for weight support.
Data Source
AI summary
A method of inferring intentions of an operator to move a robotic system includes monitoring the intention of the operator, with a controller. The intention of the operator is inferred to be one of a desired acceleration and a desired deceleration. The intention of the operator is also as a desired velocity. Admittance parameters are modified as a function of at least one of the inferred acceleration, deceleration, and velocity.