Hoist Motor Dynamic Torque Control for Impact Mitigation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Industrial machines like electric rope shovels experience increased stress and structural fatigue due to sudden impact loading during digging operations, which can lead to weld cracking and reduced operational life, as conventional methods are inadequate in dynamically managing these impacts.
Innovation Solution
A control system that actively monitors the acceleration of the hoist motor and compensates for motor inertia by sending a reverse torque control signal to mitigate the impact loading, thereby reducing fatigue on machine structures and increasing the nominal allowable bail pull during digging operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional static impact control methods are used, then the machine structure is designed to withstand expected impact loads, but the machine experiences increased stress and structural fatigue during sudden impact loading
Solution Approach 1:
The patent applies dynamics by transitioning from static impact control design to dynamic control. The system continuously monitors hoist motor acceleration and dynamically adjusts the torque command signal in real-time based on actual operating conditions. This allows the control system to adapt to varying impact scenarios rather than relying on fixed design margins, thereby reducing stress and fatigue while maintaining structural integrity.
Solution Approach 2:
The patent implements feedback control by monitoring the actual acceleration of the hoist motor and using this information to adjust the torque command signal. The controller compares the measured acceleration against expected values and modifies the torque command accordingly to limit impact loading. This closed-loop feedback mechanism enables real-time optimization of impact control, improving both reliability and operational life.
2Object-affected harmful factors
If slip clutches are used to limit impact load, then the impact load is reduced, but the control system becomes more complex and less precise
Solution Approach 1:
The patent replaces mechanical impact limiting devices like slip clutches with an electronic control system. Instead of using mechanical elements to physically limit torque through friction or slipping, the system uses a controller to electronically adjust the torque command signal based on monitored acceleration. This substitution reduces mechanical complexity while providing more precise and adjustable impact control.
Solution Approach 2:
The patent changes the control parameter from fixed mechanical torque limiting to dynamic electronic torque adjustment. The controller modifies the torque command signal parameter in real-time based on measured acceleration, allowing flexible and precise control of impact loads without the complexity of mechanical limiting devices. This parameter-based control enables adaptive response to varying operating conditions.
3Speed
If the hoist motor applies maximum programmed torque to compensate for speed reduction, then the speed is maintained, but the impact loading on the motor and machine structures increases significantly
Solution Approach 1:
The patent applies preliminary anti-action by detecting the onset of impact loading through acceleration monitoring and preemptively adjusting the torque command signal to counteract the harmful effects. When sudden deceleration is detected, the controller reduces the torque command to prevent excessive impact forces from developing, thereby protecting the motor and structures while maintaining adequate speed control.
Solution Approach 2:
The patent uses partial action by applying only the necessary torque to maintain speed control during impact events, rather than always applying maximum programmed torque. The controller dynamically adjusts the torque level based on actual conditions, applying sufficient torque to maintain operational performance while avoiding the excessive torque that would create harmful impact loads on the motor and structures.
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 dynamic control system effectively limits the damaging effects of impact loading, reducing stress on the hoist rope, gear case, and other structural elements, while increasing the nominal loading capacity of the machine, thus extending its operational life.
Implementation Method 1
the majority of the inertia of the entire machine is concentrated in the hoist motor that moves the dipper. Due to this inertia, when the hoist motor starts having a large negative acceleration (i.e., deceleration) based on the applied load, this creates a an additional torque
Data Source
AI summary
A method of controlling a digging operation of an industrial machine. The industrial machine includes a dipper, a hoist rope attached to the dipper, a hoist motor moving the hoist rope and the dipper, and a computer having a controller. The method includes monitoring a speed of the hoist motor, determining an acceleration rate of the hoist motor, comparing the acceleration rate of the hoist motor to a threshold reverse factor, determining an impact situation when the acceleration rate is less than the threshold reverse factor, and sending a reverse torque control command signal to the hoist motor.