CVT Control System for Forklift Engine Power Optimization
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Solution Overview
Problem
Modern industrial equipment, such as forklifts, equipped with continuously variable transmissions (CVTs), face challenges in optimizing engine power output and efficiency due to the need for precise coordination between engine power and transmission ratios, which is not effectively addressed by existing technologies.
Innovation Solution
A control system that coordinates engine power output with CVT ratios using a controller to manage engine speed and torque, employing a gain scheduled approach to adjust transmission ratios based on vehicle velocity, engine speed, and driver inputs, ensuring optimal power and efficiency by preventing engine stalling and managing power demands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a CVT is used to provide continuous transmission ratios, then the adaptability of the transmission system is improved, but the difficulty of coordinating engine power output with transmission ratios increases
Solution Approach 1:
The control system dynamically adjusts transmission ratios based on real-time operating conditions including vehicle velocity, engine speed, and driver inputs. The system continuously monitors these parameters and modifies the CVT ratio to maintain optimal engine operation within the operating envelope, resolving the contradiction by making the control system adaptive rather than static.
Solution Approach 2:
The system employs feedback mechanisms where the controller receives information about actual vehicle velocity, engine speed, and driver inputs, then adjusts the transmission ratio accordingly. This closed-loop control ensures the engine operates optimally while managing the complexity through systematic feedback processing.
2Productivity
If engine speed and torque are tightly controlled to optimize power output, then the productivity is improved, but the risk of engine stalling increases
Solution Approach 1:
The control system takes preliminary action by establishing an operating envelope that defines safe and optimal engine operation boundaries before actual operation begins. The controller uses this pre-defined envelope to guide transmission ratio selection, ensuring the engine remains within safe operating limits while optimizing power output, thus preventing stalling before it can occur.
Solution Approach 2:
The system provides beforehand cushioning by maintaining a safety margin within the operating envelope. The controller monitors engine parameters and adjusts transmission ratios to keep the engine operating away from critical boundaries, creating a buffer zone that prevents stalling while still allowing optimal power output.
3Measurement precision
If the transmission ratio is adjusted based on multiple parameters (velocity, engine speed, driver inputs), then the precision of power optimization is improved, but the device complexity increases
Solution Approach 1:
The controller serves multiple functions simultaneously: it monitors vehicle velocity, engine speed, driver inputs, and transmission ratio; it determines the operating envelope; it calculates optimal transmission ratios; and it commands the CVT actuator. This multi-functionality consolidates complexity into a single universal control unit rather than requiring separate systems for each function.
Solution Approach 2:
The system achieves precise power optimization by dynamically changing multiple parameters (transmission ratio, engine speed, vehicle velocity) in coordination. The controller adjusts these parameters based on their interrelationships, using the operating envelope framework to manage the complexity of multi-parameter coordination while maintaining high precision.
Data Source
AI summary
A control system for a vehicle uses one or more inputs of a velocity request, a brake request, a speed request, travel direction indication, engine speed, and vehicle speed to determine a control strategy for a continuously variable transmission. A target engine speed is selected based upon the inputs, and the engine and continuously variable transmission ratio are controlled to achieve the target engine speed while controlling the vehicle according to the inputs. In some embodiments, the control strategy further selects the target engine speed according to accessory system demands, such as a hoist or lift system.