Steering Mechanism for Electric Zero-Turn Mowers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing electric zero turn radius (ZTR) steering and brake interfaces for lawn mowers lack the feedback resistance and mechanical feel provided by hydraulic systems, making them less intuitive for operators.
Innovation Solution
A steering lever mechanism with a pivot assembly, position-measuring device, mechanical resistance, and cam follower system that mimics the feedback and resistance of hydraulic systems, including a sensor for activating the parking brake, to replicate the driving feel of hydraulic-based systems in an electric interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If an electric steering interface is used for zero turn radius lawn mowers, then the system complexity and energy consumption are reduced compared to hydraulic systems, but the feedback resistance and mechanical feel provided to the operator are lost
Solution Approach 1:
A mechanical resistance device is introduced as an intermediary component between the electric steering interface and the operator. This device provides the necessary feedback resistance and mechanical feel without requiring a complete hydraulic system, thus resolving the contradiction by adding a minimal mechanical element to an otherwise electric system.
Solution Approach 2:
The steering interface is segmented into distinct functional components: the electric steering mechanism for primary control, and a separate mechanical resistance device for providing feedback. This segmentation allows each component to perform its specialized function efficiently, maintaining system simplicity while restoring tactile feedback.
2Ease of operation
If a mechanical resistance device is added to the electric steering interface, then the feedback resistance and mechanical feel are restored, but the device complexity increases
Solution Approach 1:
The mechanical resistance device is designed to provide resistance only in specific steering positions (particularly at neutral and extreme positions) rather than throughout the entire steering range. This localized approach to providing mechanical feedback minimizes the complexity of the resistance mechanism while still achieving the desired operational feel.
Solution Approach 2:
The mechanical resistance device replicates the essential characteristics of hydraulic feedback resistance without copying the entire hydraulic system. It creates a simplified model of the hydraulic feel using mechanical elements, thus providing the necessary feedback while maintaining lower system complexity.
3Ease of operation
If the cam follower system is used to provide mechanical resistance, then the feedback resistance is enhanced, but the manufacturing precision requirements increase
Solution Approach 1:
The cam follower system is designed with inherent compliance and tolerance compensation. The follower can move dynamically within the cam profile, allowing for variations in manufacturing precision without significantly affecting the overall feedback characteristics. This dynamic design approach reduces the stringency of manufacturing precision requirements.
Solution Approach 2:
The cam profile is designed with cushioning regions that anticipate and compensate for manufacturing variations. By incorporating built-in compliance zones in the cam design, the system tolerates manufacturing imprecisions while still providing consistent feedback resistance to the operator.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides an electric ZTR steering and brake interface that closely replicates the feedback and resistance experience of hydraulic systems, enhancing operator control and comfort by using a pivot assembly, position-measuring device, and cam follower system, while ensuring precise control and engagement of the parking brake.
Implementation Method 1
The cam follower is spring biased for engaging one of the first or second recesses of the cam member
Implementation Method 2
A mechanical resistance device connects between pivot assembly and the frame of the mower vehicle for resisting rotation of the pivot assembly and the lever assembly between the forward position and the rear position
Data Source
AI summary
A steering lever mechanism for a mower vehicle includes a lever assembly and a base which is fixed to the mower vehicle for mounting the lever assembly to the mower. The lever assembly includes a pivot assembly and a lever portion. The lever portion is pivotably mounted to the pivot assembly for rotation about a longitudinal axis between an inboard position and an outboard position. The pivot assembly is also pivotably mounted to the base for rotation of the pivot bracket portion and the lever portion about a transverse axis between a rear position, an intermediate neutral position and a forward position. A rotation-measuring device is associated with the base and the pivot assembly for measuring the forward and rear rotation of the lever assembly.