Robotic Load Handling Torque Control for Smooth Grid Movement
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Solution Overview
Problem
Existing load handling devices in storage systems experience instability and jerky movements on grid structures due to uneven wheel rotation and acceleration, which can damage items being transported.
Innovation Solution
A load handling device with a wheel assembly driven by a controller that calculates and compensates torque demands using a predetermined motion control profile, combining feedforward and feedback torque control to ensure smooth movement, and adjusts torque distribution between wheels based on real-time measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional wheel assembly control is used, then the load handling device can move on the grid structure, but the movement becomes unstable and jerky due to uneven wheel rotation
Solution Approach 1:
The controller receives real-time position measurements from position detection means and uses this feedback to compensate torque demands. The system continuously monitors actual position and adjusts wheel torque to maintain stable movement, resolving the contradiction between stability and smooth operation.
Solution Approach 2:
The controller calculates feedforward torque demands based on a predetermined motion control profile before movement occurs. This preliminary torque calculation, combined with real-time feedback compensation, ensures smooth acceleration and deceleration while maintaining stability throughout the motion sequence.
2Productivity
If high acceleration is applied to move the load handling device quickly, then productivity increases, but item damage risk increases due to jerky movements
Solution Approach 1:
The system dynamically adjusts torque distribution to each wheel based on real-time position feedback and predetermined motion profiles. This enables controlled acceleration and deceleration sequences that maximize movement speed while preventing jerky motions that could damage transported items.
Solution Approach 2:
The controller modifies torque parameters dynamically during movement, transitioning between different torque levels based on the motion phase (acceleration, constant velocity, deceleration). This parameter adjustment ensures high productivity during constant velocity while protecting items during acceleration and deceleration phases.
3Device complexity
If individual wheel torque is not compensated, then device complexity is reduced, but manufacturing precision of motion control deteriorates
Solution Approach 1:
The position detection means provides continuous feedback on the load handling device's position, which the controller uses to compensate torque demands for each wheel. This feedback mechanism achieves precise position control without requiring overly complex control algorithms, balancing simplicity and precision.
Data Source
AI summary
A load handling device for lifting and moving containers stacked in a storage system having a grid framework structure supporting a plurality of tracks arranged in a grid pattern, the load handling device including: a wheel assembly driven by a drive mechanism; a lifting device for lifting a storage container; a position detection detector; and a controller configured to control movement of the load handling device by: a) determining a feedforward torque demand on the wheel assembly at a given time from a predetermined motion control profile; and b) compensating the feedforward torque demand from a measured position of the load handling device on the grid structure at the given time to calculate a torque demand on the wheel assembly.