Sensor Assembly for Torque and Angular Position Measurement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing sensor assemblies for determining the angular position and torque of a rotatable shaft are prone to wear, limited in measurement accuracy, susceptible to interference, and require significant space and high manufacturing costs, especially when using potentiometers, magnetic sensors, or optical sensors.
Innovation Solution
A sensor assembly that combines angle resolvers with inductive and magnetic sensors, utilizing a vernier principle and a direct coating strain sensor, which are arranged on a circuit board to provide accurate and interference-insensitive measurements, and a connection line for transmitting torque signals without wireless telemetry or sliding contacts, allowing for precise and cost-effective simultaneous measurement of angular position and torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If potentiometers are used for angular position measurement, then the device is simple and cost-effective, but the measurement accuracy is limited to a few angular degrees and the components are subject to wear and failure
Solution Approach 1:
The patent combines multiple sensor types (inductive sensors and magnetic sensors) with gear mechanisms to achieve high measurement precision while maintaining manufacturing feasibility. The inductive sensors detect positional information from gear teeth, and magnetic sensors provide additional measurement redundancy, together overcoming the limitations of single sensor types.
Solution Approach 2:
The patent replaces wear-prone mechanical potentiometers with non-contact inductive and magnetic sensors that read positional information from gear structures. This substitution eliminates sliding contacts and wear while achieving angular resolution far beyond the few degrees limitation of potentiometers.
2Measurement precision
If magnetic sensors are used for angular position measurement, then the measurement accuracy is improved, but the sensors can have a negative influence on one another causing distortion of the measurement result
Solution Approach 1:
The patent combines inductive sensors and magnetic sensors in a hybrid measurement system. The inductive sensors read from gear teeth while magnetic sensors provide complementary measurement. This combination allows the system to achieve high accuracy while using fewer magnetic sensors than would be needed alone, reducing mutual interference.
Solution Approach 2:
The gear structure serves as an intermediary that translates shaft position into detectable patterns for both inductive and magnetic sensors. This mechanical intermediary allows the sensors to measure position indirectly through the gear's physical structure, reducing direct sensor-sensor interference while maintaining measurement accuracy.
3Measurement precision
If optical sensors are used for angular position measurement, then the measurement accuracy is improved, but the sensor units require a comparatively large installation space and are sensitive to dirt and temperature
Solution Approach 1:
The patent replaces optical sensors with inductive and magnetic sensors that use electromagnetic fields instead of light. This substitution eliminates the need for optical paths, lenses, and scales that occupy large spaces, while achieving comparable or sufficient measurement accuracy for steering applications.
Solution Approach 2:
The patent uses small gear teeth structures that can be locally manufactured on the steering shaft or intermediate gears. These compact gear features work with closely-spaced inductive sensors, achieving high measurement accuracy in a minimal installation space without the bulky optical components.
4Measurement precision
If a direct coating strain sensor is used for torque measurement, then the measurement accuracy is improved and the sensor is resistant to interference, but the sensor requires a complex direct coating process with multiple layers
Solution Approach 1:
The direct coating strain sensor serves multiple functions: it provides structural reinforcement to the shaft, protects against corrosion, and simultaneously measures torque through its deformation properties. This multi-functionality justifies the complex coating process by eliminating the need for separate measurement devices.
Solution Approach 2:
The sensor uses a composite coating structure with conductive layers, insulating layers, and protective layers. Each layer serves a specific function: the conductive layer detects strain, the insulating layer protects electrical components, and the protective layer provides environmental resistance. This composite structure achieves high measurement accuracy and durability.
5Ease of operation
If wireless telemetry or sliding contacts are used for transmitting torque signals, then the installation is simplified, but the system is prone to interference and wear
Solution Approach 1:
The patent replaces sliding contacts and wireless telemetry with a direct electrical connection through the shaft's structural components. The strain sensor signals are conducted through embedded wires or conductive paths within the shaft structure, eliminating contact wear and electromagnetic interference while maintaining installation simplicity.
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 a cost-effective, space-saving, and accurate method for determining the angular position and torque of a rotatable shaft, offering improved measurement precision and resistance to interference and environmental factors, while eliminating the need for complex installation and maintenance.
Implementation Method 1
a first sensor unit is arranged on the main rotor and is designed as an inductively acting sensor and has an induction rotor that rotates with the main rotor and a stationary stator
Implementation Method 2
a second sensor unit is arranged on the auxiliary rotor and is designed as a magnetically acting sensor comprising a sensor element and a magnetic body, wherein the sensor element is designed to detect a movement of the magnetic body
Implementation Method 3
a strain gauge as a direct coating for torque measurement is known from DE 10 2012 208 492 A1. The direct coating consists of a metallic material with an insulating layer applied and a deformation-sensitive layer placed on top
Implementation Method 4
Ruse, H. et al: 'Magnetische Drehmomentmessung mit Low-Cost Sensor' describes a method for torque measurement in which the change in permeability of the material of a rotating shaft is detected by a sensor. This is possible using the magnetoelastic effect of ferromagnetic materials
Data Source
AI summary
The present disclosure relates to a sensor assembly for simultaneously capturing an angular position and a torque of a rotatable shaft. The sensor assembly comprises, for determining the angular position, a main body, two additional bodies, which are arranged coupled for rotation on the main body, and two angle resolvers, which are arranged on a circuit board in the immediate vicinity of the additional bodies. In this arrangement, the angles of the additional bodies are determined by the angle resolvers and passed as an angle signal to an evaluation unit arranged on the circuit board. The sensor assembly further comprises a direct coating, which captures a torque signal from the rotating shaft and passes this signal over a connection line to the evaluation unit. The connection line has a section wound multiple times around the shaft to permit a rotation of the shaft by at least +/−900°.