Hoist Motor Load Detection via Torque Analysis
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Solution Overview
Problem
Material handling systems face challenges in accurately measuring load weights, especially when using external weighing devices or current measurement systems, which are costly and prone to inaccuracies due to mechanical strain and varying load conditions during lifting and lowering operations.
Innovation Solution
A method and apparatus that utilize four measured operating conditions to determine load weight by storing torque parameters at different speeds and loads, allowing the motor drive to calculate load weight based on torque measurements, even during acceleration or constant speed operations, and transmitting load information between multiple hoist motors to ensure overall system capacity is not exceeded.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external weighing devices (load cells) are used to measure load weight, then measurement accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces mechanical weighing devices (load cells) with an electrical measurement system that uses motor current and voltage signals processed through a motor drive controller. The controller calculates load weight by analyzing the relationship between motor electrical parameters and mechanical output, eliminating the need for separate mechanical sensing equipment.
2Productivity
If load measurement is performed during acceleration or deceleration, then continuous monitoring capability is improved, but measurement accuracy deteriorates due to dynamic forces
Solution Approach 1:
The motor drive controller continuously monitors motor current, voltage, and speed signals, and uses feedback algorithms to distinguish between current consumed for acceleration and current consumed for supporting the load weight. By processing the relationship between electrical input and mechanical output in real-time, the system can calculate accurate load weight measurements even during dynamic operation.
3Power
If multiple hoisting motors are used to lift a load, then lifting capacity is improved, but determining total load weight becomes more complex
Solution Approach 1:
The patent combines the measurement systems of multiple hoisting motors into a unified load assessment approach. The motor drive controller receives electrical parameter signals from all motors, processes them collectively, and determines the total load weight by summing the individual load contributions calculated from each motor's electrical characteristics, thereby simplifying the overall measurement architecture.
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
Enables periodic and accurate load monitoring without external devices, ensuring safe operation by comparing calculated load weights to rated capacities, preventing overloads and allowing for precise weight determination in varying load conditions.
Implementation Method 1
A method and apparatus for measuring the load in a material handling system using one or more motor drives to lift a load
Data Source
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AI summary
A system and method for determining the load in a materia! handling system is disclosed. The load weight detection system measures torque at four operating conditions both at constant speed and during acceleration. The level of torque generated by the motor under each of these operating conditions is stored in the motor drive, The motor drive also receives a signal corresponding to the speed of the hoist motor. Based on the measured torque, as well as the expected torque at no load and at rated load for the measured speed, the motor drive then determines the load present on the hoist. In some systems, two or more hoists are required to operate in tandem to lift a load. Each motor drive determines the weight of the load supported by its respective hoist motor and determines a total weight of the load based on the weights determined by each motor drive.