Industrial Vehicle Speed Control via Dynamic Engine Limiting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing vehicle speed control systems for industrial vehicles, such as forklift trucks, face issues with excessive acceleration and overshoot in vehicle speed, particularly when handling loads, due to the need for increased engine speed, and struggle to balance engine power for both traveling and load handling, leading to inefficient fuel consumption and operator discomfort.
Innovation Solution
A vehicle speed control apparatus that uses PI control to determine a target engine speed based on the deviation between target and actual vehicle speeds, with an upper limit set to 5-10% above the actual engine speed, preventing excessive acceleration and overshoot by limiting the target engine speed according to actual engine conditions, ensuring sufficient power for load handling while maintaining stable vehicle speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If feedback gain is increased to ensure sufficient engine speed for load handling, then engine speed response is improved, but excessive acceleration and overshoot occur during vehicle starting
Solution Approach 1:
The patent applies dynamic control by adjusting the target engine speed based on the current operating state. Specifically, the target engine speed is set to a fixed value during starting to prevent overshoot, while during steady-state operation it is dynamically adjusted to ensure sufficient power for load handling. This state-dependent dynamic adjustment resolves the contradiction between rapid response and stability.
Solution Approach 2:
The patent changes the target engine speed parameter according to the vehicle operating condition. During starting, the target engine speed is set to a lower fixed value to prevent excessive acceleration. During steady-state operation, the target engine speed is increased to ensure sufficient power for load handling. This parameter change strategy resolves the contradiction by adapting the target speed to different operational phases.
2Power
If target engine speed is increased to provide sufficient power for load handling, then power availability is improved, but fuel consumption increases
Solution Approach 1:
The patent optimizes the target engine speed parameter to balance power availability and fuel consumption. During starting and transient phases, a lower target engine speed is used to reduce fuel consumption. During steady-state load handling, the target engine speed is increased to ensure sufficient power. This adaptive parameter adjustment resolves the contradiction between power and fuel efficiency.
Solution Approach 2:
The patent applies partial action by providing sufficient engine speed only when actually needed for load handling, rather than maintaining high engine speed continuously. During idle or low-load conditions, the engine speed is kept at a lower level to save fuel, and increased only when load handling requires additional power. This selective application resolves the contradiction between power availability and fuel consumption.
3Speed
If target engine speed is set high for rapid acceleration, then acceleration performance is improved, but overshoot in vehicle speed occurs
Solution Approach 1:
The patent applies dynamic control strategies that adjust target engine speed based on the current speed deviation. During starting when deviation is large, a moderate target speed is used to prevent overshoot. As the vehicle approaches the desired speed and deviation decreases, the target engine speed is adjusted to maintain smooth acceleration without overshooting. This dynamic adjustment resolves the contradiction between acceleration performance and control precision.
Data Source
Figure 1~2
Figure 3~4
AI summary
A vehicle speed control apparatus of an industrial vehicle has a controller that determines a target engine speed by PI control based on a deviation between a target vehicle speed and an actual vehicle speed. The controller controls an upper limit of the target engine speed according to an actual engine speed.