Slew Rotation Sensor Positioning for Thermal Error Reduction
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Solution Overview
Problem
Existing power machines, such as excavators, face challenges in precisely determining the rotational position of the upper frame portion relative to the undercarriage due to measurement errors caused by thermal effects and the susceptibility of existing sensors to such effects, which can lead to significant implement positioning errors.
Innovation Solution
The implementation of a swivel sensor positioned below the swivel barrel or proximate to the bottom of the swivel spool, which provides accurate slew position measurement by minimizing thermal effects and eliminating the need for sensor components in the center of the swivel spool, allowing for improved design and reduced measurement errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If positioning sensors are placed on the house or undercarriage, then rotational position can be detected, but measurement precision deteriorates due to thermal effects causing significant measurement errors
Solution Approach 1:
The patent extracts the sensor system from the traditional house/undercarriage mounting locations and relocates it to the swivel assembly. Specifically, a magnet is mounted on the swivel spool while a Hall effect sensor is mounted on the swivel barrel, separating the sensing components from the thermal environment of the main structural components. This extraction removes the sensors from the harmful thermal effects that cause measurement drift in conventional arrangements.
Solution Approach 2:
The patent introduces the swivel assembly components (swivel spool and swivel barrel) as intermediary elements between the rotating house and the stationary undercarriage. By mounting the magnet on the swivel spool and the Hall effect sensor on the swivel barrel, the system uses these intermediary rotating components as the reference frame for measurement, rather than directly mounting sensors on the thermally unstable house or undercarriage structures.
2Ease of operation
If electrical wires or cables are routed through the swivel joint, then power and signals can be transmitted, but device complexity increases due to the need to protect wires by limiting rotation
Solution Approach 1:
The patent replaces traditional mechanical wiring solutions with a wireless communication system. The Hall effect sensor generates electrical signals that are transmitted wirelessly to the control system, eliminating the need for physical wires or cables running through the swivel joint. This substitution removes the mechanical constraints and protection mechanisms that would otherwise be required to accommodate wire routing in a rotating assembly.
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 achieves significantly more accurate slew position measurement, essential for automated or semi-automated functions, and enhances design flexibility by reducing the need for space-consuming sensor components in the swivel assembly.
Implementation Method 1
A Hall effect sensor 404 is mounted to the swivel barrel 504 and a magnet 408 is mounted on the swivel spool 502
Data Source
AI summary
A power machine or excavator includes a swivel assembly coupling the upper frame portion to the lower frame portion, while providing accurate slew position measurement using a swivel sensor which is positioned to reduce measurement errors over a thermal range of operation of the power machine. The swivel assembly includes a swivel barrel configured to be attached to the lower frame portion of the power machine, and a swivel spool configured to be attached to the upper frame portion. The swivel sensor is positioned and configured to provide a sensor output indicative of a rotational position of the upper frame portion relative to the lower frame portion.