Inductive Position Sensor Pulse Density Modulation
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Solution Overview
Problem
Existing inductive position sensors face high power consumption and require significant signal post-processing efforts, leading to increased space requirements and complexity, particularly due to the use of PWM signals which necessitate low-pass filtering.
Innovation Solution
The use of pulse density signals as modulation signals for inductive position sensors, which allows for the generation of precise sine and cosine signals, reducing the need for extensive filtering and minimizing energy losses by applying square-wave signals for only a portion of the carrier frequency, thereby simplifying digital implementation and reducing circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If PWM signals are used for modulation in inductive position sensors, then the sensor can operate with standard modulation techniques, but significant signal post-processing effort and low-pass filtering are required, increasing device complexity and space requirements
Solution Approach 1:
The patent replaces the conventional PWM modulation approach with a novel modulation scheme that directly generates position information without requiring extensive post-processing filtering. This substitution eliminates the need for complex low-pass filter circuits and reduces the burden on signal processing hardware, thereby resolving the contradiction between ease of manufacture and device complexity.
Solution Approach 2:
The patent changes the modulation parameter from standard PWM duty cycle variation to a novel modulation approach where the position information is encoded in a manner that naturally suppresses harmonics. This parameter change allows the sensor to operate with simplified circuitry, reducing both the complexity and space requirements of the signal processing section while maintaining ease of manufacture.
2Measurement precision
If extensive low-pass filtering is applied to PWM signals, then accurate position detection can be achieved, but the circuit requires additional components and increased space in the ASIC
Solution Approach 1:
The patent substitutes the traditional approach of using large-area low-pass filter circuits with a novel modulation and detection method that achieves the same measurement precision with minimal additional components. This substitution dramatically reduces the ASIC space required while maintaining accurate position detection capability.
Solution Approach 2:
The patent employs a detection method that captures position information through a simplified signal processing path, effectively creating a functional copy of the position data without requiring the full complexity of traditional filtering approaches. This reduces the physical space needed in the ASIC while preserving measurement accuracy.
3Reliability
If square-wave signals are applied continuously over the full carrier frequency period, then complete excitation of the oscillating circuit is achieved, but power consumption increases
Solution Approach 1:
The patent applies square-wave signals in a periodic manner rather than continuously, exciting the oscillating circuit only during specific phases of the carrier frequency period. This periodic excitation maintains reliable oscillating circuit operation while significantly reducing average power consumption compared to continuous excitation, thereby resolving the contradiction between reliability and energy usage.
Solution Approach 2:
The patent implements partial excitation of the oscillating circuit by applying square-wave signals for only a portion of the carrier frequency period rather than the full period. This partial action is sufficient to maintain reliable position detection while reducing the energy consumed, effectively balancing reliability requirements with power consumption constraints.
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
This approach results in a more efficient, accurate, and compact signal processing circuit with lower power consumption and reduced space requirements, enhancing the reliability and precision of position sensing.
Implementation Method 1
two transmission units (12, 14) generate two first alternating fields (4, 5), each with a carrier frequency and a location-dependent amplitude
Implementation Method 2
the oscillating circuit 20 emits an electromagnetic alternating field of the same frequency as that of the alternating fields of the two transmitter units 12, 14, the alternating field emitted by the oscillating circuit 20 being phase-shifted with respect to the other two alternating fields
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
The invention relates to an inductive position sensor, in particular a rotational angle sensor, with two first transmitter units for the generation of two locally-varying first alternating fields with the same carrier frequency and at least one tuned circuit arranged in or on an element which may be moved within the alternating fields and the position of which is to be determined. The tuned circuit can be energised by the total alternating field and generates a tuned circuit alternating field with the same carrier frequency as the first alternating fields. The position sensor is further provided with at least one receiver unit which receives the tuned circuit alternating field and an analysis unit for determining the phase shift between the tuned circuit alternating field and at least one of the two first alternating fields, wherein the two first alternating fields may each be generated by a carrier frequency signal on which essentially the same, essentially 90° phase-shifted modulation signal is modulated. Each carrier frequency signal may be generated by application of a square-wave alternating voltage to the first transmitter units. The modulation signal is a pulse density signal with a pulse density changing with time for generation of a signal curve with an essentially sine or cosine wave form, the square wave signal being applied to the first transmitter unit for the duration of the pulse density signal.