Position detector and method for detecting position of movable element of linear motor

Abstract

To provide a position detector capable of accurately detecting the position of a movable element.SOLUTION: The position detector 200 generates a position detection signal φ indicating the position of the mover 120 of the linear motor 100. The stator has a plurality of N-pole magnets and S-pole magnets alternately arranged at a period L. The mover includes first and second magnetic sensors spaced apart from each other by L / 2 + 2kL, where k is a non-negative integer. The difference detector 210 calculates a difference signal err = sin θ * cos φ - cos θ * sin φ, where sin θ is a first signal S1 based on the output of the first sensor and cos θ is a second signal S2 based on the output of the second sensor. The loop filter 220 filters the error signal err. The integrator 230 integrates the output LFOUT of the loop filter 220 to generate a position detection signal φ that is continuous within the stroke range of the mover 120.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a position detection technique for a linear motor. [Background technology]

[0002] In order to accurately control the linear motion of a linear motor (also known as a linear actuator), it is necessary to accurately detect the moving part with high resolution. A linear motor has a stator and a mover. The stator has multiple north-pole magnets and south-pole magnets arranged alternately in the direction of movement of the mover.

[0003] In such linear motors, a known technique for detecting the position of the mover is to place two magnetic sensors on the mover side, spaced apart by a distance equivalent to a 90° phase difference. When the mover moves, the two magnetic sensors produce sine waves that are 90° out of phase with each other, i.e., orthogonal to each other. The position of the mover can be detected by using these two sine waves. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-41173

[0005] [overview] The present disclosure has been made in view of the above-mentioned problems, and one of the purposes of an embodiment thereof is to provide a position detector that can accurately detect the position of a mover.

[0006] One aspect of the present disclosure relates to a position detector that generates a position detection signal φ indicating the position of a mover of a linear motor. The linear motor includes a stator having a plurality of north-pole and south-pole magnets alternately arranged with a period L, and a mover having a first magnetic sensor and a second magnetic sensor arranged a distance L / 2+2kL, where k is a non-negative integer. The position detector includes an error detector that calculates an error signal err based on err = sin θ × cos φ - cos θ × sin φ, where sin θ is a first signal based on the output of the first magnetic sensor and cos θ is a second signal based on the output of the second magnetic sensor; a loop filter that filters the error signal err; and an integrator that integrates the output of the loop filter to generate a position detection signal φ that is continuous within the stroke range of the mover.

[0007] Another aspect of the present disclosure relates to a method for generating a position detection signal φ indicating the position of a mover of a linear motor. The linear motor includes a stator having a plurality of north-pole magnets and south-pole magnets alternately arranged with a period L, and a mover having a first magnetic sensor and a second magnetic sensor arranged a distance L / 2+2kL apart, where k is a non-negative integer. The method includes the steps of: calculating an error signal err based on err = sin θ × cos φ - cos θ × sin φ, where sin θ is a first signal based on the output of the first magnetic sensor and cos θ is a second signal based on the output of the second magnetic sensor; filtering the error signal err with a loop filter; and integrating the output of the loop filter to generate a position detection signal φ that is continuous within a stroke range of the mover.

[0008] Any combination of the above elements, or mutual substitution of elements or expressions between methods, devices, systems, etc., are also valid aspects of the present invention or the present disclosure. Furthermore, the description in this section (Means for Solving the Problems) does not explain all essential features of the present invention, and therefore, subcombinations of the described features may also constitute the present invention. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a block diagram of a positioning system according to an embodiment. [Figure 2] FIG. 2 is a diagram illustrating the first signal and the second signal. [Figure 3] FIG. 3 is a block diagram of a position detector according to the embodiment. [Figure 4] FIG. 4 is a diagram for explaining the operation of the position detector of FIG. 3, in which the horizontal axis represents time.

[0010] [Detailed explanation] (Outline of the embodiment) A summary of some exemplary embodiments of the present disclosure is provided. This summary is intended to provide a simplified overview of some concepts of one or more embodiments in order to provide a basic understanding of the embodiments as a prelude to the more detailed description that follows. It is not intended to limit the scope of the invention or disclosure. Furthermore, this summary is not an exhaustive overview of all possible embodiments, nor does it limit essential elements of the embodiments. For convenience, the term "one embodiment" may refer to one embodiment (example or variant) or multiple embodiments (examples or variants) disclosed herein.

[0011] In this specification, the linear motor is not limited to one with a straight track, but also includes one with a curved track and one with a closed curve such as a circle or ellipse.

[0012] One aspect of the present disclosure relates to a position detector that generates a position detection signal φ indicating the position of a mover of a linear motor. The linear motor includes a stator having a plurality of north-pole and south-pole magnets alternately arranged with a period L, and a mover having a first magnetic sensor and a second magnetic sensor arranged a distance L / 2+2kL, where k is a non-negative integer. The position detector includes an error detector that calculates an error signal err based on err = sin θ × cos φ - cos θ × sin φ, where sin θ is a first signal based on the output of the first magnetic sensor and cos θ is a second signal based on the output of the second magnetic sensor; a loop filter that filters the error signal err; and an integrator that integrates the output of the loop filter to generate a position detection signal φ that is continuous within the stroke range of the mover.

[0013] This configuration enables accurate position detection by using quadrature detection. Furthermore, the position detection signal φ is generated as a continuous value within the stroke range of the mover, eliminating the need for unwrapping processing.

[0014] In one embodiment, the integrator may integrate the output of the loop filter to a first order.

[0015] In one embodiment, the integrator may perform a second integration on the output of the loop filter.

[0016] In one embodiment, the position detector may be monolithically integrated on a single semiconductor substrate. "Monolithically integrated" includes cases where all of the circuit components are formed on a semiconductor substrate, or where the main circuit components are monolithically integrated, and some resistors and capacitors for adjusting circuit constants may be provided outside the semiconductor substrate. By integrating the circuit on a single chip, the circuit area can be reduced and the characteristics of the circuit elements can be maintained uniform.

[0017] In one embodiment, the position detector may be integrated into a driver circuit that drives the linear motor, or may be integrated into a controller that controls the driver circuit.

[0018] (Embodiment) Preferred embodiments will be described below with reference to the drawings. The same or equivalent components, parts, and processes shown in each drawing will be designated by the same reference numerals, and redundant descriptions will be omitted where appropriate. Furthermore, the embodiments are merely examples and do not limit the invention, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.

[0019] In this specification, "a state in which component A is connected to component B" includes not only a case in which component A and component B are directly physically connected to each other, but also a case in which component A and component B are indirectly connected to each other via other components that do not substantially affect the electrical connection between them or that do not impair the function or effect achieved by their connection.

[0020] Similarly, "a state in which component C is provided between component A and component B" includes not only cases in which components A and C, or components B and C, are directly connected, but also cases in which they are indirectly connected via other components that do not substantially affect the electrical connection state between them or impair the functions or effects achieved by their combination.

[0021] 1 is a block diagram of a positioning system 2 according to an embodiment. The positioning system 2 includes a linear motor 100, a position detector 200, and a controller 300.

[0022] The linear motor 100 includes a stator 110 and a mover 120. The stator 110 includes a plurality of permanent magnets 112. The plurality of permanent magnets 112 includes north pole magnets and south pole magnets that are alternately arranged at a period L in the direction in which the mover 120 moves.

[0023] The mover 120 has a first magnetic sensor 122 and a second magnetic sensor 124. The first magnetic sensor 122 and the second magnetic sensor 124 are arranged at a distance L / 2 apart in the moving direction of the mover 120. In general, the distance between the first magnetic sensor 122 and the second magnetic sensor 124 may be L / 2+2kL, where k is a non-negative integer.

[0024] The position detector 200 generates a position detection signal φ indicating the position θ of the movable element 120 in the movable direction, using a first signal S1 based on the output of the first magnetic sensor 122 and a second signal S2 based on the output of the second magnetic sensor 124.

[0025] 2 is a diagram illustrating the first signal S1 and the second signal S2. When the mover 120 moves, the first signal S1 and the second signal S2 become two sine waves with a phase difference of 90°. When the position of the mover is θ, the two signals S1 and S2 can be expressed as follows: S1=sinθ S2=cosθ

[0026] 3 is a block diagram of a position detector 200 according to an embodiment. The position detector 200 includes an error detector 210, a loop filter 220, and an integrator 230. When the first signal S1 is sin θ and the second signal S2 based on the output of the second magnetic sensor is cos θ, the error detector 210 calculates an error signal err by the following equation: err=sinθ×cosφ-cosθ×sinφ

[0027] For example, the error detector 210 includes a CORDIC (Coordinate Rotation Digital Computer) 212 , a first multiplier 214 , a second multiplier 216 , and a subtractor 218 .

[0028] The CORDIC 212 calculates a third signal S3 and a fourth signal S4 based on the position detection signal φ. S3=cosφ S4=sinφ

[0029] The first multiplier 214 calculates the product P1 of the first signal S1 and the third signal S3. S1×S3=sinθ×cosφ The second multiplier 216 calculates the product P2 of the second signal S2 and the fourth signal S4. S2×S4=cosθ×sinφ

[0030] A subtractor 218 calculates the difference between the product P1 and the product P2 as an error signal err. err=P1-P2=sinθ×cosφ-cosθ×sinφ

[0031] This error signal err is equal to sin(θ-φ), and when θ=φ, err=0. Therefore, err can be understood to represent the error between θ and φ, i.e., the phase difference, and error detector 254 can be understood as a phase detector that detects the difference (phase difference) between θ and φ.

[0032] The position detector 200 can also be configured by software, in which case each block in FIG. 3 represents a function or a unit of calculation processing implemented by software.

[0033] The loop filter 220 filters the error signal err. The loop filter 220 can be configured as a PI (proportional-integral) controller (also called a compensator). The output signal LFOUT of the loop filter 220 is P and the integral coefficient K I Using this, it can be expressed by the following formula: LFOUT=K P ×err+K I ∫err dt

[0034] The integrator 230 integrates the output LFOUT of the loop filter 220 to generate the position detection signal φ. In one embodiment, the integrator 230 may perform a first-order integration of the output LFOUT of the loop filter 220. In this case, the output LFOUT of the loop filter 220 has the dimension of an angular velocity.

[0035] In one embodiment, the integrator 230 may perform a second-order integration of the output LFOUT of the loop filter 220. In this case, the output LFOUT of the loop filter 220 has the dimension of angular acceleration.

[0036] The value of the integrator 230, that is, the position detection signal φ, is continuous within the stroke range of the mover 120.

[0037] The above is the configuration of the position detector 200. Next, the operation thereof will be described.

[0038] Fig. 4 is a diagram (simulation results) for explaining the operation of position detector 200 in Fig. 3, with the horizontal axis representing time. From top to bottom, Fig. 4 shows the velocity v of the mover, the first signal S1, the second signal S2, and the position detection signal φ. With regard to the position detection signal φ, waveform (i) represents the value calculated by position detector 200 in Fig. 3, and waveform (ii) represents the value calculated by a method according to the comparative technique.

[0039] In comparative technology, φ=arctan(sinθ / cosθ)=arctan(S1 / S2) In this method, the arctangent value φ is limited to a range of -180° to 180°, resulting in discontinuities every 360°. Therefore, the position of the mover 120 within the stroke range cannot be directly determined from the position detection signal φ obtained by this comparison technique, and additional calculation processing is required.

[0040] In contrast, in the position detector 200 according to the embodiment, the position detection signal φ is continuous within the stroke range of the mover 120, and the position detection signal φ directly indicates the position of the mover 120. In other words, the additional processing required in the comparison technique is not required.

[0041] The embodiments described using specific terms merely illustrate the principles and applications of the present invention, and many modifications and changes in arrangement are permitted to the embodiments as long as they do not deviate from the spirit of the present invention as defined in the claims.

[0042] (Addendum) One aspect of the technology disclosed in this specification can be understood as follows.

[0043] (Item 1) A position detector that generates a position detection signal φ indicating the position of a mover of a linear motor, The linear motor is a stator having a plurality of north pole magnets and south pole magnets alternately arranged at a period L; a mover having a first magnetic sensor and a second magnetic sensor arranged at a distance of L / 2+2kL, where k is a non-negative integer; Including, The position detector an error detector that calculates an error signal err based on the equation err=sinθ×cosφ−cosθ×sinφ, where sinθ is a first signal based on the output of the first magnetic sensor and cosθ is a second signal based on the output of the second magnetic sensor; a loop filter for filtering the error signal err; an integrator that integrates the output of the loop filter to generate the position detection signal φ that is continuous within the stroke range of the mover; A position detector comprising:

[0044] (Item 2) Item 2. The position detector according to item 1, wherein the integrator performs a first-order integration of the output of the loop filter.

[0045] (Item 3) Item 2. The position detector according to item 1, wherein the integrator performs a second-order integration of the output of the loop filter.

[0046] (Item 4) 4. The position detector according to any one of items 1 to 3, which is monolithically integrated on a single semiconductor substrate.

[0047] (Item 5) A method for generating a position detection signal φ indicating a position of a mover of a linear motor, comprising: The linear motor is a stator having a plurality of north pole magnets and south pole magnets alternately arranged at a period L; a mover having a first magnetic sensor and a second magnetic sensor arranged at a distance of L / 2+2kL, where k is a non-negative integer; Including, The method comprises: a step of calculating an error signal err based on err=sinθ×cosφ−cosθ×sinφ, where sinθ is a first signal based on the output of the first magnetic sensor and cosθ is a second signal based on the output of the second magnetic sensor; filtering the error signal err with a loop filter; an integration step of integrating the output of the loop filter to generate the position detection signal φ that is continuous within a stroke range of the mover; A method comprising:

[0048] (Item 6) 6. The method according to claim 5, wherein the integration step is a first-order integration of the output of the loop filter.

[0049] (Item 7) 6. The method according to claim 5, wherein the integration step is a second-order integration of the output of the loop filter. [Explanation of symbols]

[0050] 2 Positioning System 100 Linear Motor 110 Stator 112 Permanent Magnets 120 Mover 122 First magnetic sensor 124 Second magnetic sensor 200 Position detector 210 Error Detector 212 CORDIC 214 First Multiplier 216 Second Multiplier 218 Subtractor 220 Loop Filter 230 Integrator 300 Controller

Claims

1. A position detector that generates a position detection signal φ indicating the position of a mover of a linear motor, The linear motor is a stator having a plurality of north pole magnets and south pole magnets alternately arranged at a period L; a mover having a first magnetic sensor and a second magnetic sensor arranged at a distance of L / 2+2kL, where k is a non-negative integer; Including, The position detector an error detector that calculates an error signal err based on the equation err=sin θ×cos φ−cos θ×sin φ, where sin θ is a first signal based on an output of the first magnetic sensor and cos θ is a second signal based on an output of the second magnetic sensor; a loop filter for filtering the error signal err; an integrator that integrates the output of the loop filter to generate the position detection signal φ, which is continuous within the stroke range of the mover; A position detector comprising:

2. The position detector according to claim 1 , wherein the integrator performs a first-order integration on the output of the loop filter.

3. The position detector according to claim 1 , wherein the integrator performs a second-order integration on the output of the loop filter.

4. 4. The position detector according to claim 1, which is monolithically integrated on a single semiconductor substrate.

5. A method for generating a position detection signal φ indicating a position of a mover of a linear motor, comprising: The linear motor is a stator having a plurality of north pole magnets and south pole magnets alternately arranged at a period L; a mover having a first magnetic sensor and a second magnetic sensor arranged at a distance of L / 2+2kL, where k is a non-negative integer; Including, The method comprises: a step of calculating an error signal err based on err=sin θ×cos φ−cos θ×sin φ, where sin θ is a first signal based on the output of the first magnetic sensor and cos θ is a second signal based on the output of the second magnetic sensor; filtering the error signal err with a loop filter; an integration step of integrating the output of the loop filter to generate the position detection signal φ that is continuous within a stroke range of the mover; A method comprising:

6. The method of claim 5 , wherein the integrating step integrates the output of the loop filter by one order.

7. The method of claim 5 , wherein the integrating step integrates the output of the loop filter twice.

Images