Jerk-Constrained Trajectory Control for Stable Load Handling Motion
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Solution Overview
Problem
Existing load handling devices in storage and fulfilment systems face challenges with stability and smooth movement, particularly during acceleration and deceleration on grid structures, which can lead to oscillation or toppling and potentially damage items being transported.
Innovation Solution
A method and system for controlling the movement of load handling devices using a computer-implemented method that generates additive lookahead for adaptive cutting feedrate control, allowing for precise control of wheel movements and stabilization through individual hub motor control and trajectory planning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If load handling devices move quickly on grid structures, then productivity is improved, but stability deteriorates causing oscillation or toppling
Solution Approach 1:
The control system dynamically adjusts wheel speeds based on real-time device state and trajectory requirements. Individual hub motors independently modulate wheel rotation speeds to maintain stability during acceleration and deceleration phases, allowing high-speed operation without compromising stability.
Solution Approach 2:
The system changes motion parameters (acceleration rates, velocity profiles) adaptively based on device state, load conditions, and trajectory characteristics. By dynamically adjusting these parameters, the system achieves high productivity while maintaining stability through optimized motion control.
2Loss of time
If acceleration and deceleration are rapid, then time efficiency is improved, but harmful factors increase causing item damage
Solution Approach 1:
The control system dynamically adjusts acceleration and deceleration parameters based on real-time conditions including device state, load characteristics, and trajectory requirements. This adaptive parameter modification enables rapid transport while limiting harmful inertial forces that could damage items.
Solution Approach 2:
The system employs dynamic motion profiling where acceleration and deceleration rates are continuously adjusted during operation. Individual wheel speed control allows smooth transitions that minimize jerky movements and impact forces on transported items.
3Stability of the object's composition
If individual wheel speed control is implemented, then stability is improved, but device complexity increases
Solution Approach 1:
The patent replaces complex mechanical differential drive mechanisms with independent electric hub motors on each wheel. This substitution uses electronic control instead of mechanical linkages, achieving individual wheel speed control while reducing mechanical complexity and improving reliability.
Solution Approach 2:
The control system manages complexity by dynamically adjusting only the necessary parameters (wheel speeds) based on real-time device state. Through adaptive control algorithms, the system achieves stable movement with minimized control complexity by focusing on critical degree of freedom adjustments.
Data Source
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AI summary
A method for generating a trajectory to control the movement of a motion device, the method comprising: i) receiving a specification of the trajectory, the specification comprising a commanded position, ii) receiving at least one jerk constraint; iii) generating a sequence of one or more trajectory segments based on the at least one jerk constraint, each of the one or more trajectory segments being a respective portion of the trajectory prescribing at least one of a jerk reference, an acceleration reference, a velocity reference and a position reference as a function of time; wherein the one or more trajectory segments of the sequence of trajectory segments is generated by applying a velocity transition algorithm comprising moving the magnitude of the velocity reference of the one or more trajectory segments in a given time to a desired final velocity reference, the difference between the desired final velocity reference and the velocity reference defining a velocity delta, wherein the velocity transition algorithm comprises computing a peak acceleration having a magnitude being a function of the velocity delta.