Conveyor Position Hold Control for Variable-Weight Items
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional control schemes struggle to accurately hold items of varying weights at their initial stopping locations during a position hold in conveying systems, leading to potential movement due to insufficient or excessive torque application.
Innovation Solution
A control apparatus estimates the size parameter, such as weight, of an item using motor current measurements, and adjusts control parameters like integral gain and proportional gain coefficients to precisely control motor torque, ensuring items remain stationary during position hold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional control schemes are used for position hold, then the control system is simple, but items of varying weights cannot be accurately held at their initial stopping locations
Solution Approach 1:
The control system dynamically adjusts control parameters (proportional gain, integral gain, integral windup limit) based on the estimated load weight. This allows the same control system to accurately handle items of varying weights by changing its parameters rather than requiring different hardware configurations, thus improving position hold accuracy without proportionally increasing device complexity
Solution Approach 2:
The system automatically estimates the load weight using motor current measurements during conveyance and self-adjusts the control parameters without external intervention. This self-service capability enables accurate position holding for varying weights while keeping the control system relatively simple, as the adaptation happens autonomously
2Reliability
If fixed control parameters are used, then the control system is simple, but items of varying weights experience insufficient or excessive torque application
Solution Approach 1:
The control system transitions from static fixed parameters to dynamic adaptive parameters that change based on the estimated load weight. The proportional gain, integral gain, and integral windup limit are all adjusted dynamically according to the actual weight being conveyed, ensuring reliable torque control across varying weights while maintaining adaptability
Solution Approach 2:
The system uses feedback from motor current measurements during the conveyance phase to estimate load weight, then applies this information to adjust control parameters for the position hold phase. This feedback loop enables the system to adapt to varying weights reliably without requiring complex pre-programming or manual configuration
3Manufacturing precision
If standard position hold control is used, then the system operates efficiently, but items may move from their initial stopping locations due to insufficient torque
Solution Approach 1:
The control system adjusts the torque level (through proportional and integral gains) based on the estimated load weight. For heavier items, higher torque is applied to prevent movement, while for lighter items, appropriate but not excessive torque is used. This adaptive parameter adjustment maintains position accuracy while optimizing energy consumption by avoiding uniformly high torque application
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 solution enhances precision and efficiency in holding items of varying weights, reducing oscillations and eliminating the need for physical stops, while maintaining items at their initial locations even in non-horizontal conveyor sections.
Implementation Method 1
An electric motor converts electrical energy into mechanical energy that is provided to a load
Implementation Method 2
A control apparatus estimates the size parameter, such as weight, of an item using motor current measurements, and adjusts control parameters like integral gain and proportional gain coefficients to precisely control motor torque, ensuring items remain stationary during position hold
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
A control apparatus for a conveying system includes: a control module configured to control a power converter coupled to a motor; and a modification module. The modification module is configured to: estimate a size parameter of an item conveyed by the motor; determine if a hold command is received; and if a hold command is received, modify one or more parameters of the control module based on the estimated size parameter of the item to thereby hold a rotor of the motor at a rotor hold position.