Adaptive Drive Control for Utility Vehicle Speed Limiting
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Solution Overview
Problem
Utility vehicle drive control systems face challenges in providing smooth accelerations, fine controllability at low speeds, and rapid response at high speeds, with existing electronic over hydraulic systems experiencing issues like jerky movements, decreased productivity, and compromised controllability due to limited speed settings and response time delays.
Innovation Solution
An adaptive drive control system that scales operator drive commands based on commanded speed and drive output, using an electronic controller to limit vehicle speed below the commanded speed until a designated threshold is reached, then ramps up power supply to achieve the commanded speed, implemented in a hydrostatic drive system with a swash plate control mechanism, where the scaling factor and threshold are pre-set and non-adjustable by the operator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If simple speed limiters are used to limit output to a percentage of maximum input, then fine controllability at low speed is improved and controls feel smoother, but maximum travel speed is limited and productivity decreases
Solution Approach 1:
The patent implements dynamic speed limiting where the limit is not fixed but adapts based on operating conditions. The controller automatically adjusts the speed limit between a first value (lower) and a second value (higher) based on detected operating conditions, allowing the system to provide fine control when needed while maintaining high speed capability when productivity is prioritized, eliminating the need for manual operator intervention
Solution Approach 2:
The system changes the speed limit parameter dynamically based on operating conditions. Rather than using a fixed percentage limit, the controller modifies the speed limit parameter automatically, transitioning between different limit values to optimize both controllability and productivity for different operational scenarios
2Ease of operation
If transient drive system output limits are applied that gradually increase from 70% to 100% over time, then smoother controls are achieved, but control resolution at lower speeds is not improved
Solution Approach 1:
The patent applies different control characteristics to different operating ranges. The controller provides enhanced control resolution specifically at lower speeds while maintaining smooth acceleration characteristics, rather than applying a uniform acceleration curve across all speed ranges. This allows fine control where needed without compromising overall smoothness
3Adaptability or versatility
If user-selectable drive response with preset acceleration rates is provided, then operator choice is improved, but response time increases and machine operation becomes sluggish
Solution Approach 1:
The system eliminates the need for operator selection by implementing automatic detection and adjustment of speed limits based on operating conditions. The controller autonomously determines the appropriate speed limit value and applies it without requiring operator intervention or choice, thereby maintaining fast response times while still providing adaptability to different operational scenarios
Data Source
AI summary
A utility vehicle such as a loader includes a drive control system that includes an electronic controller and a manually actuated drive command device, such as one or more joysticks. The electronic controller is configured to control the drive control system to supply propulsive power at a predetermined output that is lower than that which is commanded by the drive command device for so long as an output of the drive control system is beneath a designated threshold, maintaining vehicle speed lower than a commanded vehicle speed. The electronic controller is further configured to control the drive control system to ramp up the propulsive power supply toward that which is commanded by the drive command device when the output of the drive control system is above the designated threshold, causing the vehicle speed to approach a commanded vehicle speed. The vehicle may include a EH drive system such as a hydrostatic drive system.