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EP-4148430-B1 - FAULT TOLERANT SERVO SENSOR WITH LINEAR HALL SENSORS AND DISCRETE HALL SENSORS

EP4148430B1EP 4148430 B1EP4148430 B1EP 4148430B1EP-4148430-B1

Inventors

  • LONG, GEOFFREY ALAN
  • VIELE, BRIAN ROBERT

Dates

Publication Date
20260506
Application Date
20170201

Claims (9)

  1. A system, comprising an output shaft (1102); a brushless motor having a motor shaft (1104); a set of gears (1106), wherein the output shaft is coupled to the motor shaft via the set of gears; a rotor coupled to the motor shaft, and configured to rotate through a plurality of sectors each corresponding to a range of angles representing a portion of a 360° rotation; a plurality of discrete Hall sensors (1104; 1110) provided in the motor; and a processor configured to: initialize (1300) at least an output shaft angle associated with the output shaft to a known value; determine (1302) a direction of rotation associated with the motor shaft using the plurality of discrete Hall sensors in the motor by receiving (1400), from the plurality of discrete Hall sensors, a current rotor position of the rotor and comparing (1402) the current rotor position against a previous rotor position in order to determine the direction of rotation, wherein the previous rotor position is a sector in the plurality of sectors that is adjacent to the current rotor position; and update (1304) the output shaft angle from the known value using an incremental value and the direction of rotation, wherein the incremental value is proportional to a gear ratio of the set of gears; wherein the rotor position is determined to be within one of the plurality of sectors by a particular combination of discrete Hall sensor output values.
  2. The system recited in claim 1, wherein updating (1304) the output shaft angle includes: in the event the direction of rotation is a first direction, incrementing (1502) a previous output shaft angle with the incremental value in order to obtain a current output shaft angle; and in the event the direction of rotation is a second direction, decrementing (1504) the previous output shaft angle with the incremental value in order to obtain the current output shaft angle.
  3. The system recited in claim 1, wherein the brushless motor includes a plurality of stationary windings and a plurality of permanent magnets in the rotating part of the motor, wherein the plurality of stationary windings act against the plurality of permanent magnets.
  4. The system recited in claim 1, wherein previous state information, including a previousrotor position or a previous output shaft angle, is used to determine the direction of rotation associated with the motor shaft.
  5. The system recited in claim 1, further comprising: an aircraft including aerodynamic control surfaces; and a servo controlling movement of the aerodynamic control surfaces, wherein the servo comprises the output shaft.
  6. A method, comprising: initializing (1300) at least an output shaft angle associated with an output shaft to a known value, wherein the output shaft is coupled to a motor shaft of a brushless motor via a set of one or more gears; determining (1302) a direction of rotation associated with the motor shaft using a plurality of discrete Hall sensors in the brushless motor by receiving (1400), from the plurality of discrete Hall sensors, a current rotor position of a rotor coupled to the motor shaft, and comparing (1402) the current rotor position against a previous rotor position in order to determine the direction of rotation, wherein the rotor is configured to rotate through a plurality of sectors each corresponding to a range of angles representing a portion of a 360° rotation, wherein the previous rotor position is a sector in the plurality of sectors that is adjacent to the current rotor position; and updating (1304) the output shaft angle from the known value using an incremental value and the direction of rotation, wherein the incremental value is proportional to a gear ratio of the set of one or more gears.
  7. The method recited in claim 6, wherein updating (1304) the output shaft angle includes: in the event the direction of rotation is a first direction, incrementing (1502) a previous output shaft angle with the incremental value in order to obtain a current output shaft angle; and in the event the direction of rotation is a second direction, decrementing (1504) the previous output shaft angle with the incremental value in order to obtain the current output shaft angle.
  8. The method recited in claim 6, wherein the brushless motor includes a plurality of stationary windings and a plurality of permanent magnets in the rotating part of the motor, wherein the plurality of stationary windings act against the plurality of permanentmagnets.
  9. The method recited in claim 6, wherein the direction of rotation associated with the motor shaft is determined based on previous state information, including a previous rotor position or a previous output shaft angle.

Description

BACKGROUND OF THE INVENTION One type of sensor for measuring the angle of an output shaft (e.g., in an aircraft or an automobile) uses four linear Hall sensors packaged in a single integrated circuit (IC) and a diametrically magnetized disk (i.e., a magnet) oriented above the IC which contains the Hall sensors. The magnet is typically mounted to the output shaft of the servo and the IC is typically mounted on a printed circuit board (PCB) normal to the output shaft axis. To provide redundancy, some IC manufacturers produce ICs with two sets of four Hall sensors (e.g., for a total of eight sensors). However, since both sets of sensors are packaged in the same IC, such sensors are vulnerable to common mode failures (e.g., both sets of Hall sensors are unavailable if the IC loses power). New techniques for measuring the angle of a shaft (e.g., with less vulnerability to common mode failures) would be desirable. DE 10 2004 061405 A1 describes a motor vehicle having a vehicle battery and an internal combustion engine with a donor disk which is coupled to a crankshaft of the internal combustion engine. US 2010/052663 A1 describes a sensor unit for a rotary encoder which serves for detecting the rotary movements of a drive shaft in both directions and which has a single-stage transmission with an input gear which is arranged concentrically with respect to and is non-rotatably connected to the drive shaft. US 2009/140731 A1 describes a multiple-rotation absolute-value encoder of a geared motor, wherein the geared motor reduces the rotational speed of a motor shaft and takes it out from a gear shaft to drive a machine device in an operating range corresponding to the two rotations of the gear shaft. DE 10 2014 113493 A1 describes a truck with a steering control and at least one steering angle sensor having a magnetic element bearing input shaft and two sensor units, one of which cooperates as a powered Hall sensor unit and a non-energized magnetic sensor unit with the magnetic element to detect its rotation. SUMMARY According to an aspect of the present invention, there is provided a system according to any of claims 1 to 5. According to another aspect of the present invention, there is provided a method according to any of claims 6 to 9. BRIEF DESCRIPTION OF THE DRAWINGS Various embodiments and examples of the invention are disclosed in the following detailed description and the accompanying drawings. Figure 1A is a diagram illustrating an example of a servo sensor with two sets of linear Hall sensors from a side view.Figure 1B is a diagram illustrating an example of a servo sensor with two sets of linear Hall sensors from a top view.Figure 2 is a diagram illustrating another type of servo sensor which is more vulnerable to common mode failure.Figure 3 is a flowchart illustrating an example of a process to estimate an angle using two or more sets of linear Hall sensors.Figure 4 is a diagram illustrating an example of a servo sensor with three sets of linear Hall sensors.Figure 5 is a diagram illustrating an example of a PCB with three ICs with linear Hall sensors.Figure 6 is a graph illustrating an example of values measured by three sets of linear Hall sensors as a function of angle.Figure 7 is a block diagram of a system which uses three sets of linear Hall sensors to measure an angle and monitoring the health of the system.Figure 8 is a flowchart illustrating an example of a process to estimate an angle using three or more sets of linear Hall sensors.Figure 9 is a flowchart illustrating an example of a process to generate a health status signal.Figure 10 is a diagram illustrating an example of a servo sensor with four sets of linear Hall sensors.Figure 11 is a diagram illustrating an embodiment of a motor with discrete Hall sensors which are used to measure the angle of an output shaft.Figure 12 is a diagram illustrating an embodiment of related positions of a rotor in a motor shaft and angles of an output shaft.Figure 13 is a flowchart illustrating an embodiment of a process to estimate an angle using a plurality of discrete Hall sensors.Figure 14 is a flowchart illustrating an embodiment of a process to determine a direction of rotation associated with the motor shaft.Figure 15 is a flowchart illustrating an embodiment of a process to update an output shaft angle using an incremental value and a direction of rotation associated with a motor shaft. DETAILED DESCRIPTION The invention can be implemented in numerous ways, including as a process; an apparatus; a system; a composition of matter; a computer program product embodied on a computer readable storage medium; and/or a processor, such as a processor configured to execute instructions stored on and/or provided by a memory coupled to the processor. In this specification, these implementations, or any other form that the invention may take, may be referred to as techniques. In general, the order of the steps of disclosed processes may be altered within the sco