JP2011107062A - Rotation angle detecting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique capable of outputting a detection result and of being usable more without fail, in a calculation portion for calculating the rotation angle of a rotor. <P>SOLUTION: A device includes a first rotation angle sensor and a second rotation angle sensor for detecting respective rotation angle of a first driven gear and a second driven gear rotated by a torque applied thereto from a gear attached to the rotor, and an ECU for operating a rotation angle of the rotor based on detection results inputted from the first rotation angle sensor and the second rotation angle sensor. At least either of the first rotation angle sensor or the second rotation angle sensor outputs a pulse width modulation signal having a duty ratio, corresponding to the detected rotation angle so that either the edge of a leading edge or a trailing edge becomes a period determined in advance, and a time acquired by adding a time TP determined in advance to a time corresponding to the detected rotation angle is set as the time from one edge until the other edge. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a rotation angle detection device.

Conventionally, an apparatus for detecting the rotation angle of a rotating body that can rotate over 360 degrees has been proposed.
For example, Patent Document 1 describes a rotation angle detection device configured as follows. That is, the rotatable rotating body has a gear having n teeth. This gear is engaged with a gear having m teeth and two gears having m + 1 teeth. The angles ψ and θ of these two gears are measured using two periodic angle sensors. This measurement is performed in a contact or non-contact manner. Each of these angle sensors is connected to an electronic evaluation circuit, and this evaluation circuit performs a calculation necessary for detecting the rotation angle φ of the rotating body. In the rotation angle detection device configured as described above, the two angle sensors, which are so-called absolute value sensors, supply the rotation angles ψ and θ of the two gears at the time of switch-on immediately after the rotation angle detection device is switched on. . The angle φ of the rotating body is detected from these angle values, the angle marks or the number of teeth of the gears of the rotating body, and the angle marks or the number of teeth of the two gears.

Japanese Patent No. 3792718

  The rotation angle of each of the two driven gears that mesh with the gear attached to the rotating body that can rotate over 360 degrees is detected by detection means such as two sensors, and the rotating body is based on the detection results of these two sensors. In the apparatus for calculating the rotation angle, it is conceivable to use detection means for outputting a pulse width modulation signal having a duty ratio corresponding to the measured rotation angle, as the two detection means.

  In the case of using detection means for outputting a pulse width modulation signal, the detection means outputs the detection result so that it can be used more reliably in a calculation unit that calculates the rotation angle of the rotating body based on the detection result. It is desirable.

  For this purpose, the present invention is a rotation angle detection device for detecting the rotation angle of a rotating body, the first driven body and the second driven body rotating in conjunction with the rotation of the rotating body, First detection means for detecting the rotation angle of the first follower, second detection means for detecting the rotation angle of the second follower, the first detection means, and the second detection Rotation angle calculation means for calculating the rotation angle of the rotating body based on the detection result input by the means, and at least one of the first detection means and the second detection means is the detected rotation. A pulse width modulation signal having a duty ratio according to the angle is output so that one of the rising edge and the falling edge has a predetermined cycle, and at a time corresponding to the detected rotation angle, Constant The resulting time obtained by adding the time which is a rotation angle detection device, characterized in that the time from one edge the to the other edge.

Here, the period of the pulse width modulation signal output by at least one of the first detection unit and the second detection unit is substantially the same as the period in which the rotation angle calculation unit calculates the rotation angle of the rotating body. It is preferable that
Further, the apparatus further comprises moving means for starting counting at one edge of the pulse width modulation signal and counting to the other edge and moving the count value taken in a predetermined register to a predetermined storage area, Preferably, the rotation angle calculation means calculates the rotation angle of the rotating body based on the count value moved to the predetermined storage area by the moving means.

Further, the rotation angle calculation means and the movement means are the same computer, and the computer sets the count value in advance after ensuring a processing cycle for controlling an electric motor that applies a rotation assisting force to the rotating body. It is preferable to move to a predetermined storage area and calculate the rotation angle of the rotating body at a predetermined cycle.
The rotating body includes a gear, the first driven body includes a first driven gear, and the second driven body has a number of teeth different from the number of teeth of the first driven gear. The first driven body and the second driven body have a second driven gear, and the first driven gear and the second driven gear are applied with a rotational force by the gear. It is preferable to rotate in conjunction with the rotation of the rotating body.

  According to the present invention, as compared with the case where the present invention is not adopted, the rotation angle calculation means outputs so that the detection result of at least one of the first detection means and the second detection means can be used more reliably. can do.

It is a schematic block diagram of the rotation angle detection apparatus which concerns on this Embodiment. It is a figure which shows the relationship between the rotation angle of a rotary body, and the rotation angle of a 1st driven gear and a 2nd driven gear. It is a figure which shows the relationship between the rotation angle of a 1st driven gear and a 2nd driven gear, and the duty ratio of a pulse width modulation signal. It is a figure which shows the relationship between the rotation angle of a 1st driven gear and a 2nd driven gear, and the pulse width modulation signal which a 1st rotation angle sensor and a 2nd rotation angle sensor output. It is a flowchart which shows the procedure of the rotation angle calculation process of the rotary body which ECU performs. It is a figure which shows schematic structure of the electric power steering apparatus which concerns on this Embodiment. It is a schematic block diagram of the part which controls an EPS apparatus. It is a schematic block diagram of a target current calculation part. It is a schematic block diagram of a control part. It is a figure which shows the reference example of the relationship between the rotation angle of a 1st driven gear and a 2nd driven gear, and the duty ratio of a pulse width modulation signal. It is a figure which shows an example of the output mode of the pulse width modulation signal in the case of the reference example shown in FIG. It is a figure which shows the relationship with the other process in case ECU performs the movement process which moves a count value to RAM as the highest priority interruption process. It is a figure which shows the pulse width modulation signal of the 1st rotation angle sensor and 2nd rotation angle sensor which concern on this Embodiment. It is a figure which shows the relationship between the pulse width modulation signal of the 1st rotation angle sensor and 2nd rotation angle sensor which concern on this Embodiment, and the process of ECU.

Hereinafter, this embodiment will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic configuration diagram of a rotation angle detection device 1 according to the present embodiment.
The rotation angle detection device 1 is a device that detects the rotation angle of a rotating body 100 that is rotatably supported by a body frame of a vehicle such as an automobile. The rotating body 100 can be exemplified by a steering shaft 202 described later, for example, and can be attached to the housing via a bearing such as a ball bearing fixed to a housing (not shown) which is a member fixed to the main body frame. It is rotatably supported.

  The rotation angle detection device 1 detects the rotation angle of the rotating body 100 to detect the rotation angle of the steering wheel 201 (see FIG. 6) connected to the rotating body 100, and consequently the steering wheel 201 (see FIG. 6). ) Can be used to grasp the direction of travel of the vehicle. The detection result of the rotation angle detection device 1 is used in various control devices such as a device that performs route guidance and a device that changes the hardness of the suspension according to the steering angle.

Below, the rotation angle detection apparatus 1 is explained in full detail.
The rotation angle detection device 1 includes a gear 101 that is an example of a gear attached to the rotating body 100, a first driven gear 111 that is an example of a first driven gear that meshes with the gear 101, and a second that meshes with the gear 101. And a second driven gear 121 as an example of the driven gear. For example, the first driven gear 111 is rotatable with respect to the housing by being attached to the first rotation shaft 110 that is rotatably supported by the housing. The second driven gear 121 is also rotatable with respect to the housing, for example, by being attached to the second rotating shaft 120 that is rotatably supported by the housing. The first driven gear 111 and the first rotating shaft 110 constitute an example of a first driven body, and the second driven gear 121 and the second rotating shaft 120 constitute an example of a second driven body. Constitute.

FIG. 2 is a diagram illustrating the relationship between the rotation angle of the rotating body 100 and the rotation angles of the first driven gear 111 and the second driven gear 121.
The number of teeth of the gear 101 is n, the number of teeth of the first driven gear 111 is m, and the number of teeth of the second driven gear 121 is (m + 1). Then, the relationship between the number of teeth of the gear 101 and the number of teeth of the first driven gear 111 and the relationship between the number of teeth of the gear 101 and the number of teeth of the second driven gear 121 are taken into account, and the first driven gear 111 is taken into consideration. 2 and the number of teeth of the second driven gear 121 is (m + 1), the rotation angle of the rotating body 100 and the first driven gear 111, as shown in FIG. The figure which shows the relationship with the rotation angle of the 2nd driven gear 121 can be obtained. It can be exemplified that n is 81 and m is 21.

Further, the rotation angle detection device 1 includes a first rotation angle sensor 112 as an example of first detection means for detecting the rotation angle of the first driven gear 111. The first rotation angle sensor 112 is arranged outside the first driven gear 111 in the radial direction of rotation, and a plurality of first rotation angle sensors 112 are formed in the teeth of the first driven gear 111 or in the circumferential direction of the first rotary shaft 110. Based on the angle mark, the rotation angle of the first driven gear 111 is detected.
Similarly, the rotation angle detection device 1 has a second rotation angle sensor 122 as an example of second detection means for detecting the rotation angle of the second driven gear 121. The second rotation angle sensor 122 is disposed outside the second driven gear 121 in the rotation radial direction, and a plurality of second rotation angle sensors 122 are formed in the circumferential direction of the second driven gear 121 or the second rotation shaft 120. Based on the angle mark, the rotation angle of the second driven gear 121 is detected.
Then, the rotation angle detection device 1 is based on the output values from the first rotation angle sensor 112 and the second rotation angle sensor 122, in other words, by the first rotation angle sensor 112 and the second rotation angle sensor 122. An electronic control unit (hereinafter simply referred to as “ECU”) 10 (see FIG. 1) as an example of a rotation angle calculation means for calculating the rotation angle of the rotating body 100 based on the input detection result is provided. .

The first rotation angle sensor 112 and the second rotation angle sensor 122 respectively generate a pulse width modulation signal PWM having a duty ratio corresponding to the detected rotation angle of the first driven gear 111 or the second driven gear 121. Output at a predetermined cycle.
FIG. 3 is a diagram showing the relationship between the rotation angles of the first driven gear 111 and the second driven gear 121 and the duty ratio of the pulse width modulation signal PWM.
As shown in FIG. 3, the first rotation angle sensor 112 and the second rotation angle sensor 122 respectively set the rotation angles 0 to 360 degrees of the first driven gear 111 or the second driven gear 121 as duty cycles. It is converted into a pulse width modulation signal PWM with a ratio of D1% to D2% and output.

FIG. 4 shows the relationship between the rotation angle of the first driven gear 111 and the second driven gear 121 and the pulse width modulation signal PWM output from the first rotation angle sensor 112 and the second rotation angle sensor 122. FIG.
As shown in FIG. 4, the first rotation angle sensor 112 generates a pulse width modulation signal PWMA having an ON (High) pulse time PWMA_ON corresponding to the rotation angle of the first driven gear 111 with a predetermined period. The second rotation angle sensor 122 outputs the pulse width modulation signal PWMB having an ON (High) pulse time PWMB_ON according to the rotation angle of the second driven gear 121, and outputs the pulse width modulation signal PWMB in a predetermined cycle PWMB_T. To output.

  The ECU 10 is an arithmetic logic circuit including a CPU, ROM, RAM, backup RAM, and the like. A first rotation angle sensor 112 and a second rotation angle sensor 122 are connected to the ECU 10, and electric power is supplied to the first rotation angle sensor 112 and the second rotation angle sensor 122 via the ECU 10. . The ECU 10 also receives the pulse width modulation signals PWMA and PWMB output from the first rotation angle sensor 112 and the second rotation angle sensor 122, and the period of the pulse width modulation signals PWMA and PWMB and the pulse width modulation signal. The PWMA and PWMB ON (High) pulse times PWMA_ON and PWMB_ON are recognized.

More specifically, the ECU 10 includes a timer counter for measuring the period of the pulse width modulation signals PWMA and PWMB, and two for measuring the time of the ON (High) pulse of each of the pulse width modulation signals PWMA and PWMB. A total of three timer counters including a timer counter are provided.
The timer counter for measuring the periods of the pulse width modulation signals PWMA and PWMB is set to a free-run counter, and takes the value of the counter at the rising edge of the pulse width modulation signals PWMA and PWMB into the capture register. Also, using the buffer function, the current (n-th) count values TA (n) and TB (n) of the pulse width modulation signals PWMA and PWMB, and the previous (n-1th) count value TA (n−1) ) And TB (n−1) can be stored in a RAM (memory).
Each timer counter for measuring the time of the ON (High) pulse of each of the pulse width modulation signals PWMA and PWMB starts at the rising edge of the pulse width modulation signal PWMA or PWMB, stops at the falling edge, The value (count value) is taken into the capture register and the counter is cleared.

  Then, the ECU 10 moves the count values of the latest pulse width modulation signals PWMA and PWMB, which are captured in the capture register, to the RAM (memory). And ECU10 performs the calculation process which calculates rotation angle (phi) of the rotary body 100 based on the count value memorize | stored in RAM with the predetermined period T (refer FIG. 4). In FIG. 4, a process for calculating a rotation angle φ of the rotating body 100 performed by the ECU 10 and a cycle (PWMA_T and PWMB_T) and timing at which the first rotation angle sensor 112 and the second rotation angle sensor 122 detect the rotation angle. The timing and the processing cycle T are shown.

Hereinafter, the rotation angle calculation process of the rotating body 100 performed by the ECU 10 will be described using a flowchart.
FIG. 5 is a flowchart showing the procedure of the rotation angle calculation process of the rotating body 100 performed by the ECU 10. The ECU 10 performs this rotation angle calculation process at the period T described above.
The ECU 10 first calculates the detection periods PWMA_T and PWMB_T of the first rotation angle sensor 112 and the second rotation angle sensor 122 (step 501).
The process of calculating the detection period PWMA_T of the first rotation angle sensor 112 is performed based on the counter value TA (n) at the falling edge of the current (n-th) pulse width modulation signal PWMA stored in the RAM. This is a process of subtracting the counter value TA (n−1) at the falling edge of the (n−1) th pulse width modulation signal PWMA (PWMA_T = TA (n) −TA (n−1)).
In addition, the process of calculating the detection cycle PWMB_T of the second rotation angle sensor 122 starts from the counter value TB (n) at the falling edge of the current (n-th) pulse width modulation signal PWMB, the previous (n-1th). ) Is subtracted from the counter value TB (n−1) at the falling edge of the pulse width modulation signal PWMB (PWMB_T = TB (n) −TB (n−1)).

Thereafter, the ECU 10 calculates the rotation angle θA of the first driven gear 111 and the rotation angle θB of the second driven gear 121 (step 502).
The processing for calculating the rotation angle θA of the first driven gear 111 reads the ON pulse time PWMA_ON of the pulse width modulation signal PWMA corresponding to the latest rotation angle of the first driven gear 111 stored in the RAM, and This is a process of calculating by substituting into the equation (1) and substituting the detection cycle PWMA_T calculated at step 501 into the following equation (1).
θA = (PWMA_ON−PWMA_T × 0.05) / (PWMA_T × 0.9) × K1 (1)
Here, K1 is a coefficient for converting the pulse width modulation signal PWMA to the rotation angle θA, and is a coefficient depending on the width of the duty ratio used for the pulse width modulation signal PWMA and the maximum rotation angle of 360 degrees. It is remembered.

Further, the process of calculating the rotation angle θB of the second driven gear 121 reads the ON pulse time PWMB_ON of the pulse width modulation signal PWMB corresponding to the latest rotation angle of the second driven gear 121 stored in the RAM, This is a process of substituting into the following formula (2) and calculating by substituting the detection cycle PWMB_T calculated at step 501 into the following formula (2).
θB = (PWMB_ON−PWMB_T × 0.05) / (PWMB_T × 0.9) × K2 (2)
Here, K2 is a coefficient for converting the pulse width modulation signal PWMB into the rotation angle θB, and is a coefficient depending on the width of the duty ratio used for the pulse width modulation signal PWMB and the maximum rotation angle of 360 degrees. It is remembered.
In the present embodiment, the relationship between the width of the duty ratio used for pulse width modulation signal PWMB and the maximum rotation angle 360 degrees is the relationship between the width of the duty ratio used for pulse width modulation signal PWMA and the maximum rotation angle 360 degrees. Since the relationship is the same, it is preferable that K2 = K1.

  Thereafter, the ECU 10 calculates an angle difference ΔθAB between the rotation angle θA of the first driven gear 111 calculated in step 502 and the rotation angle θB of the second driven gear 121 (ΔθAB = θA−θB) (step 503). ). Then, the ECU 10 determines whether or not the angle difference ΔθAB calculated in step 503 is smaller than 0 degrees (deg) (step 504). If the determination in step 504 is affirmative, the value obtained by adding 360 degrees to the angle difference ΔθAB calculated in step 503 is replaced with ΔθAB (ΔθAB = ΔθAB + 360) (step 505), and the process proceeds to step 506. On the other hand, if a negative determination is made in step 504, the process proceeds to step 506.

In step 506, the ECU 10 calculates the rotation angle φ of the rotating body 100. This is a process of calculating by the following equation (3).
φ = ΔθAB × K3 (3)
Here, K3 is a coefficient for converting the angle difference ΔθAB between the rotation angle θA of the first driven gear 111 and the rotation angle θB of the second driven gear 121 into the rotation angle φ of the rotating body 100. The coefficient depends on the number of teeth, the number of teeth of the first driven gear 111, the number of teeth of the second driven gear 121, and 360 degrees that are detection angles of the first rotation angle sensor 112 and the second rotation angle sensor 122. Yes, it is a coefficient stored in the ROM in advance.
Thus, when the ECU 10 executes the rotation angle calculation process, the rotation angle detection device 1 detects the rotation angle φ of the rotating body 100.

ECU10 which concerns on this Embodiment mentioned above functions also as a control apparatus which controls the electric power steering apparatus 2 mentioned later. Hereinafter, the electric power steering apparatus 2 will be described.
FIG. 6 is a diagram showing a schematic configuration of the electric power steering apparatus 2 according to the present embodiment.
The electric power steering device 2 (hereinafter sometimes simply referred to as “EPS device 2”) is a steering device for arbitrarily changing the traveling direction of the vehicle. In the present embodiment, the configuration is applied to an automobile. Illustrated.

  The EPS device 2 includes a wheel-like steering wheel (handle) 201 operated by a driver, and a steering shaft 202 provided integrally with the steering wheel 201. The steering shaft 202 and the upper connection shaft 203 are connected via a universal joint 203a, and the upper connection shaft 203 and the lower connection shaft 208 are connected via a universal joint 203b.

  The EPS device 2 includes a tie rod 204 connected to each of the left and right front wheels 250 as rolling wheels, and a rack shaft 205 connected to the tie rod 204. The EPS device 2 also includes a pinion 206a that forms a rack and pinion mechanism together with rack teeth 205a formed on the rack shaft 205. The pinion 206a is formed at the lower end of the pinion shaft 206.

  The EPS device 2 also has a steering gear box 207 that houses the pinion shaft 206. The pinion shaft 206 is connected to the lower connection shaft 208 via a torsion bar (not shown) in the steering gear box 207. Inside the steering gear box 207, a torque sensor 209 is provided as an example of a steering torque detecting means for detecting the steering torque of the steering wheel 201 based on the relative angle between the lower connecting shaft 208 and the pinion shaft 206.

The EPS device 2 also includes an electric motor 210 supported by the steering gear box 207 and a speed reduction mechanism 211 that reduces the driving force of the electric motor 210 and transmits it to the pinion shaft 206.
The EPS device 2 includes a motor current detector 33 (see FIG. 9) that detects the magnitude and direction of the actual current that actually flows through the electric motor 210, and a motor voltage detector that detects the voltage across the terminals of the electric motor 210. 260.
The EPS device 2 is controlled by the ECU 10 described above. The ECU 10 receives the output value of the torque sensor 209, the output value of the vehicle speed sensor 270 that detects the vehicle speed of the automobile, and the output value of the motor voltage detection unit 260.

  The EPS device 2 configured as described above detects the steering torque applied to the steering wheel 201 by the torque sensor 209, drives the electric motor 210 in accordance with the detected torque, and generates the generated torque of the electric motor 210. It is transmitted to the pinion shaft 206. Thereby, the torque generated by the electric motor 210 assists the driver's steering force applied to the steering wheel 201.

Next, control of the EPS device 2 performed by the ECU 10 will be described.
FIG. 7 is a schematic configuration diagram of a portion that controls the EPS device 2.
The ECU 10 calculates a target auxiliary torque based on the torque signal Td, and calculates a target current required for the electric motor 210 to supply the target auxiliary torque, and a target current calculation unit 20 And a control unit 30 that performs feedback control based on the calculated target current.

FIG. 8 is a schematic configuration diagram of the target current calculation unit 20.
The target current calculation unit 20 includes a base current calculation unit 21 that calculates a base current that serves as a reference for setting the target current, an inertia compensation current calculation unit 22 that calculates a current for canceling the moment of inertia of the electric motor 210, and the like. It has. Further, the target current calculation unit 20 estimates the rotation speed of the electric motor 210 based on the damper compensation current calculation unit 23 that calculates the current that limits the rotation of the motor, the motor current signal Im, and the voltage signal Vm between the motor terminals. And a motor rotation speed estimation unit 24. Further, the target current calculation unit 20 includes a final target current determination unit 25 that determines a final target current based on outputs from the base current calculation unit 21, the inertia compensation current calculation unit 22, the damper compensation current calculation unit 23, and the like. I have.

The target current calculation unit 20 includes a vehicle speed signal v obtained by converting the vehicle speed detected by the vehicle speed sensor 270 into an output signal, and a motor obtained by converting the voltage detected by the motor voltage detection unit 260 into an output signal. A voltage signal Vm between the terminals, a motor current signal Im obtained by converting the actual current detected by the motor current detector 33 into an output signal, and a torque signal obtained by converting the torque detected by the torque sensor 209 into an output signal Td is input.
The ECU 10 receives a signal from the vehicle speed sensor 270 or the like as an analog signal, so the analog signal is converted into a digital signal by an A / D converter (not shown) and is taken into the target current calculator 20.

FIG. 9 is a schematic configuration diagram of the control unit 30.
The control unit 30 includes a motor drive control unit 31 that controls the operation of the electric motor 210, a motor drive unit 32 that drives the electric motor 210, and a motor current detection unit 33 that detects the actual current that actually flows through the electric motor 210. have.
The motor drive control unit 31 performs feedback control based on the deviation between the target current calculated by the target current calculation unit 20 and the actual current supplied to the electric motor 210 detected by the motor current detection unit 33. A feedback (F / B) control unit 40 and a PWM signal generation unit 60 that generates a PWM (pulse width modulation) signal for PWM driving the electric motor 210 are included.

The feedback control unit 40 includes a deviation calculating unit 41 for obtaining a deviation between the target current calculated by the target current calculating unit 20 and the actual current detected by the motor current detecting unit 33, and the deviation becomes zero. And a feedback (F / B) processing unit 42 for performing feedback processing.
The deviation calculation unit 41 outputs a deviation value between the target current signal IT, which is an output value from the target current calculation unit 20, and the motor current signal Im, which is an output value from the motor current detection unit 33, as a deviation signal 41a.

The feedback (F / B) processing unit 42 performs feedback control so that the target current and the actual current match. For example, the input deviation signal 41a is proportionally processed by a proportional element. A signal obtained by the integration processing by the integration element is output, and the addition calculation unit adds these signals to generate and output a feedback processing signal 42a.
The PWM signal generation unit 60 generates the PWM signal 60a based on the output value from the feedback control unit 40, and outputs the generated PWM signal 60a.

The motor drive unit 32 drives a motor drive circuit 70 in which four power field effect transistors are connected in an H-type bridge circuit configuration, and drives the gates of two field effect transistors selected from the four. And a gate drive circuit unit 80 for switching the field effect transistor. The gate drive circuit unit 80 selects two field effect transistors according to the steering direction of the steering wheel 201 based on the PWM signal (drive control signal) 60a output from the PWM signal generation unit 60, and selects the selected 2 The field effect transistors are switched.
The motor current detection unit 33 detects the value of the motor current (armature current) flowing in the electric motor 210 from the voltage generated at both ends of the shunt resistor 71 connected in series with the motor drive circuit 70, and outputs the motor current signal Im. To do.

  As described above, the ECU 10 includes the target current calculation unit 20, the control unit 30, and the like, calculates the target auxiliary torque, and calculates and calculates the target current necessary for the electric motor 210 to supply the target auxiliary torque. A series of EPS control processes for controlling the operation of the electric motor 210 such as feedback control based on the target current and generation of a PWM (pulse width modulation) signal are executed.

  That is, the ECU 10 executes the EPS control process and the rotation angle calculation process of the rotating body 100. The ECU 10 also executes background processing for performing communication processing with an external device. As described above, the ECU 10 executes a plurality of processes, and among them, the EPS control process is set to be performed with priority over other processes, and the EPS control process is prioritized over other processes at a predetermined cycle. It is set to run. Then, assuming that the ECU 10 executes the EPS control process at a predetermined cycle, various coefficients used for the EPS control process such as a coefficient used for calculating the target current and a coefficient used for feedback control are determined.

The first rotation angle sensor 112 and the second rotation angle sensor 122 of the rotation angle detection device 1 are configured as follows so that the ECU 10 can execute the EPS control process at a predetermined cycle. .
That is, the first rotation angle sensor 112 determines the time PWMA_ON of the ON pulse of the pulse width modulation signal PWMA as a time T1 corresponding to the rotation angle of the first driven gear 111 and a predetermined time TP not depending on the rotation angle. Is output as the time obtained by adding. Similarly, the second rotation angle sensor 122 determines the ON pulse PWMB_ON time of the pulse width modulation signal PWMB as a time T2 corresponding to the rotation angle of the second driven gear 121 and a predetermined time that does not depend on the rotation angle. Output as the time when TP is added.

This is due to the following reason. Since the first rotation angle sensor 112 and the second rotation angle sensor 122 are the same, the first rotation angle sensor 112 will be described below as a representative.
For example, the first rotation angle sensor 112 sets the time PWMA_ON of the ON pulse to only the time T1 corresponding to the rotation angle of the first driven gear 111 without adding the predetermined time TP, and the duty ratio is 5 Consider the case of% to 95% (D1 = 5, D2 = 95). FIG. 10 is a diagram illustrating a reference example of the relationship between the rotation angles of the first driven gear 111 and the second driven gear 121 and the duty ratio of the pulse width modulation signal PWM.

FIG. 11 is a diagram illustrating an example of an output mode of the pulse width modulation signal PWM in the reference example illustrated in FIG. 10.
As described above, the ECU 10 moves the count value of the time PWMA_ON of the ON pulse of the pulse width modulation signal PWMA taken into the capture register by the timer counter to the RAM (memory). Also, the timer counter immediately captures the counter value at the falling edge into the capture register. Therefore, when the interval for capturing the count value into the capture register is short, the time required to move the count value to the RAM is eliminated, and the count value of the capture register is based on the next falling edge before the shift. The count value may be overwritten. For example, when the rotation angle of the first driven gear 111 changes from 359.9 degrees to 0 degrees, that is, when the duty ratio changes suddenly from about 95% to 5%, the first rotation angle sensor 112 The interval between the falling edges to be output is very short (see FIG. 11. For example, when PWMA_T = 1 ms, the shortest time between the edges is 100 μs). If the count value based on is not moved to the RAM, the count value based on the falling edge having a duty ratio of about 5% is overwritten. As a result, the ECU 10 calculates the rotation angle φ of the rotating body based on the times of different ON pulses PWMA_ON, so that the detection accuracy of the rotation angle φ of the rotating body is deteriorated.

It is also possible for the ECU 10 to cope with such a problem by performing the movement process for moving the count value to the RAM as the highest priority interrupt process and prioritizing other processes.
FIG. 12 is a diagram illustrating a relationship with other processes when the ECU 10 performs a movement process of moving the count value to the RAM as the highest priority interrupt process.
When the ECU 10 performs the movement process as the highest priority interrupt process, the ECU 10 executes the movement process with the interrupt even while the ECU 10 is executing the EPS control process. Therefore, as shown in FIG. The processing cycle will fluctuate. As a result, the accuracy of the EPS control process may be reduced.

  Therefore, in the present embodiment, even if the ECU 10 executes the EPS control process at a predetermined cycle, the first rotation is performed so that a sufficient time can be secured for performing the movement process. In order to increase the interval between the falling edges output from the angle sensor 112, the first rotation angle sensor 112 determines the ON pulse time PWMA_ON of the pulse width modulation signal PWMA according to the rotation angle of the first driven gear 111. The time T1 and the predetermined time TP are added to be output. FIG. 13 is a diagram showing pulse width modulation signals PWMA and PWMB of the first rotation angle sensor 112 and the second rotation angle sensor 122 according to the present embodiment.

  The predetermined time TP is determined so that the time necessary for performing the movement process can be sufficiently secured even when the ECU 10 executes the EPS control process at a predetermined cycle. For example, it can be exemplified that the predetermined time TP is half of the period PWMA_T of the pulse width modulation signal PWMA. As a result, the duty ratio is at least 50%, and it is possible to secure at least half the period PWMA_T as the time interval for performing the movement process.

  Then, the period PWMA_T is made as long as possible. This is because if the predetermined time TP is simply added to the ON pulse time PWMA_ON while keeping the period PWMA_T the same, the time according to the rotation angle is finer than when the predetermined time TP is not added. This is because the pulse width modulation signal PWMA cannot be output. Therefore, it is preferable to lengthen the predetermined period PWMA_T of the time TP. For example, when half the period PWMA_T is added to the time of the ON pulse PWMA_ON as a predetermined time TP, the period PWMA_T is set to be twice the period PWMA_T when the predetermined time TP is not added. Is preferred.

  However, the period PWMA_T needs to be equal to or less than the processing period T of the rotation angle calculation process in order to calculate the rotation angle of the rotating body 100 with high accuracy. Therefore, in the present embodiment, the cycle PWMA_T is set to be the same as the processing cycle T of the rotation angle calculation process, and the ECU 10 executes the EPS control process at a predetermined cycle for a predetermined time TP. Also, it is determined so that a sufficient time required for performing the movement process can be secured. For example, when the processing period T of the rotation angle calculation process is 2 ms, the period PWMA_T is set to 2 ms, the predetermined time TP is set to 1 ms, and the rotation angle of the first driven gear 111 is 0 degrees to 360 degrees. Is converted into a pulse width modulation signal PWM having a duty ratio of 50% to 95% (time T1 corresponding to a rotation angle of 0 degree is 0, and time T1 corresponding to a rotation angle of 360 degrees is 900 μs). By configuring the first rotation angle sensor 112 and the second rotation angle sensor 122 in this way, the rotation angle 0 degrees to 360 degrees of the first driven gear 111 is set to the duty ratio in the cycle PWMA_T = 1 ms. While maintaining the same resolution as the configuration of converting and outputting the pulse width modulation signal PWM of 5% to 95% (time corresponding to the rotation angle 0 degree is 50 μs, time corresponding to the rotation angle 360 degrees is 950 μs), at least, It is possible to secure a time interval corresponding to a period of a configuration in which the predetermined time TP is not added.

FIG. 14 is a diagram showing a relationship between the pulse width modulation signals PWMA and PWMB of the first rotation angle sensor 112 and the second rotation angle sensor 122 according to the present embodiment and the processing of the ECU 10.
As described above, by configuring the first rotation angle sensor 112 and the second rotation angle sensor 122, the ECU 10 performs an EPS control process in a predetermined cycle (for example, 250 μs) as shown in FIG. The count value fetched into the capture register can be reliably moved to the RAM, and the rotation angle of the rotating body 100 can be calculated based on the count value. Therefore, it is possible to appropriately control the electric motor 210 and to detect the rotation angle of the rotating body 100 with high accuracy.

DESCRIPTION OF SYMBOLS 1 ... Rotation angle detection apparatus, 2 ... Electric power steering apparatus, 10 ... ECU, 20 ... Target electric current calculation part, 30 ... Control part, 100 ... Rotating body, 101 ... Gear, 110 ... 1st rotating shaft, 111 ... 1st 1 driven gear, 112... First rotation angle sensor, 120... Second rotation shaft, 121... Second driven gear, 122... Second rotation angle sensor, 201. ... Torque sensor, 210 ... Electric motor, 260 ... Motor voltage detector, 270 ... Vehicle speed sensor

Claims (5)

A rotation angle detection device for detecting a rotation angle of a rotating body,
A first driven body and a second driven body that rotate in conjunction with the rotation of the rotating body;
First detection means for detecting a rotation angle of the first follower;
Second detection means for detecting a rotation angle of the second follower;
A rotation angle calculation means for calculating a rotation angle of the rotating body based on the detection result input by the first detection means and the second detection means;
With
At least one of the first detection unit and the second detection unit has a pulse width modulation signal having a duty ratio corresponding to the detected rotation angle, and either one of the rising edge and the falling edge is set in advance. Rotation characterized in that it is output so as to have a predetermined cycle, and a time obtained by adding a predetermined time to a time corresponding to the detected rotation angle is a time from the one edge to the other edge. Angle detection device.   The cycle of the pulse width modulation signal output by at least one of the first detection unit and the second detection unit is substantially the same as the cycle in which the rotation angle calculation unit calculates the rotation angle of the rotating body. The rotation angle detection device according to claim 1. A moving unit that starts counting at one edge of the pulse width modulation signal and moves the count value counted to the other edge and taken in a predetermined register to a predetermined storage area;
3. The rotation according to claim 1, wherein the rotation angle calculation unit calculates a rotation angle of the rotating body based on a count value moved to the predetermined storage area by the moving unit. Angle detection device.   The rotation angle calculating means and the moving means are the same computer, and the computer secures a cycle of a process for controlling an electric motor that applies a rotation assisting force to the rotating body and determines the count value in advance. The rotation angle detection device according to claim 3, wherein the rotation angle of the rotating body is calculated at a predetermined cycle while being moved to the storage area. The rotating body has a gear;
The first driven body has a first driven gear;
The second driven body has a second driven gear having a number of teeth different from the number of teeth of the first driven gear;
The first driven body and the second driven body rotate in conjunction with the rotation of the rotating body by applying a rotational force to the first driven gear and the second driven gear by the gear. The rotation angle detection device according to claim 1, wherein the rotation angle detection device is a rotation angle detection device.

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