JP7576971B2 - Position detection device for moving objects, rotation amount detection device for motors - Google Patents

Description

The present invention relates to a device for detecting the position of a moving object driven by a motor, and a device for detecting the amount of rotation of the motor.

For example, an electric seat (moving body) installed in a vehicle is driven by a motor that rotates by operating a switch, and moves in the front-back and left-right directions parallel to the floor of the vehicle compartment. The amount of movement of the electric seat is determined by the amount of rotation of the motor, so in order to perform stopping control to stop the seat at a specified position, it is necessary to calculate the amount of rotation of the motor.

A method that uses a rotation sensor such as a rotary encoder to calculate the amount of motor rotation has been known for some time. However, there is also a method that calculates the amount of motor rotation by detecting the ripple current flowing through the motor windings without using a rotation sensor. This method calculates the amount of motor rotation by binarizing the detected ripple current and converting it into a pulse signal, and counting the number of rising and falling edges of the pulse signal. Patent documents 1 to 6 show such methods of calculating the amount of motor rotation based on the ripple current. The ripple current can be detected by using a shunt resistor provided to detect the motor current (see Patent documents 1 to 4).

When calculating the amount of motor rotation based on the ripple current, the ripple current may not be detected correctly even if the motor is rotating. For example, in the case of an electric vehicle seat, when the motor is stopped and the moving seat hits a stopper, the reaction force from the stopper causes the seat to move backward in the opposite direction to the direction of movement. Therefore, even though the motor is stopped, it rotates in the opposite direction to the seat's movement, and an induced voltage is generated in the winding. As a result, a motor current flows transiently based on the induced voltage, but the ripple current contained in this motor current has a very small amplitude compared to normal ripple currents, and the waveform is also distorted, making it difficult to detect as a normal ripple current. Therefore, the ripple current that flows due to the reverse rotation of the motor when a reaction force is generated as described above cannot be used to calculate the amount of motor rotation (in this case, the amount of reverse rotation).

The same thing can happen when an electric seat is stopped before the stopper position. In this case, even if the motor is controlled to stop, the electric seat does not stop immediately at the specified position, but stops after passing the specified position due to inertia (overrun). For this reason, the motor continues to rotate in conjunction with the movement of the seat from the time the electric seat passes the specified position until it stops. As a result, a motor current flows transiently based on the induced voltage generated in the windings, but the ripple current contained in this motor current also has a small amplitude and a distorted waveform, so it cannot be used to calculate the amount of motor rotation.

US Patent Publication No. 2010/0259249 U.S. Pat. No. 9,787,232 JP 2014-7806 A JP 2014-7807 A JP 2013-212028 A JP 2014-64424 A

As described above, when a reaction force or inertia acts on the moving body, the ripple current flowing through the motor is not detected correctly, and the amount of rotation of the motor cannot be calculated using the ripple current. As a result, it becomes impossible to detect the position of the moving body based on the amount of rotation of the motor, and the reliability of position detection decreases.

The objective of the present invention is to make it possible to detect the amount of rotation of a motor and the position of a moving object even when the ripple current flowing through the motor cannot be detected normally.

The position detection device of the present invention includes a motor driving section for driving a motor for moving the mobile body, a voltage detection section for detecting a motor voltage, which is a voltage between the terminals of the motor, a current detection section for detecting a motor current flowing through the motor, a ripple detection section for detecting a ripple current contained in the motor current, a first position detection section for calculating an amount of rotation of the motor based on the ripple current and detecting a position of the mobile body based on the amount of rotation, a second position detection section for calculating an amount of rotation of the motor based on a predetermined arithmetic expression using the motor voltage and the motor current and detecting a position of the mobile body based on the amount of rotation, and a shunt resistor for detecting the motor current by the current detection section . During a first moving period of the mobile body in which the ripple current shows a steady change, the position of the mobile body detected by the first position detection section is output, and during a second moving period of the mobile body in which the ripple current shows a transient change, the position of the mobile body detected by the second position detection section is output . Furthermore, due to the rotation of the motor during the second moving period, an induced voltage is generated between the terminals of the motor and a brake current flows through the shunt resistor. The second position detection unit calculates the amount of rotation of the motor using the induced voltage as the motor voltage and the brake current as the motor current, and detects the position of the moving body based on the amount of rotation.

The motor rotation amount detection device according to the present invention includes a motor drive unit for driving the motor, a voltage detection unit for detecting a motor voltage, which is a voltage between the terminals of the motor, a current detection unit for detecting a motor current flowing through the motor, a ripple detection unit for detecting a ripple current contained in the motor current, a first rotation amount detection unit for detecting an amount of rotation of the motor based on the ripple current, a second rotation amount detection unit for detecting the amount of rotation of the motor based on a predetermined calculation formula using the motor voltage and the motor current , and a shunt resistor for detecting the motor current by the current detection unit . In a first period in which the ripple current shows a steady change, the amount of rotation detected by the first rotation amount detection unit is output, and in a second period in which the ripple current shows a transient change, the amount of rotation detected by the second rotation amount detection unit is output. In addition, due to the rotation of the motor in the second period, an induced voltage is generated between the terminals of the motor, and a brake current flows through the shunt resistor. The second rotation amount detection unit detects the amount of rotation of the motor using the induced voltage as the motor voltage and the brake current as the motor current.

In this way, even if the ripple current flowing through the motor cannot be detected normally, for example when a reaction force acts on the moving object and the motor rotates in the reverse direction, the amount of rotation of the motor can be calculated using a specified formula. This makes it possible to detect the position of the moving object based on the calculated amount of rotation, improving the reliability of position detection.

According to the present invention, even if the ripple current flowing through the motor cannot be detected normally, it is possible to detect the amount of rotation of the motor and the position of the moving object.

1 is a block diagram showing an overall configuration of a position detection device for a moving body according to the present invention; FIG. 2 is a block diagram showing a specific configuration of a position detection unit. 4A to 4C are waveform diagrams of a motor current, a ripple current, and a ripple pulse in a steady state. FIG. 2 is a diagram illustrating the position detection of a moving object in a steady state. 4A and 4B are diagrams illustrating a reaction force acting on an electric seat. 4 is a waveform diagram of an induced voltage and a motor current generated by a reaction force. FIG. FIG. 13 is a diagram illustrating the position detection of a moving object in a transient state. 11A and 11B are diagrams illustrating an overrun of an electric seat due to inertia. FIG. 4 is a waveform diagram of a motor current and a ripple current during overrun. 1 is a block diagram showing an overall configuration of a motor rotation amount detection device according to the present invention; 4 is a block diagram showing a specific configuration of a rotation amount detection unit. FIG.

Embodiments of the present invention will now be described with reference to the drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals.

Figure 1 shows an example of a position detection device for a moving object according to the present invention. Here, an electric seat 30 for a vehicle as shown in Figure 5 is taken as an example of a moving object. The electric seat 30 moves in the front-rear direction (left-right direction in Figure 5) parallel to the floor of the vehicle compartment by operating a switch.

In FIG. 1, the position detection device 100 for a moving body includes a position detection unit 1 that detects the position of the power seat 30, a motor drive unit 2 that drives a motor M to move the power seat 30, a voltage detection unit 3 that detects the motor voltage, which is the voltage between terminals T1 and T2 of the motor M, a current detection unit 4 that detects the motor current flowing through the motor M, a ripple detection unit 5 that detects the ripple current contained in the motor current I, and a shunt resistor Rs for detecting the motor current by the current detection unit 4.

The motor drive unit 2 is provided between the power supply B and the ground G, and is composed of an H-bridge circuit (not shown) having four switching elements, and a switching circuit (not shown) that turns each switching element on and off. The motor drive unit 2 drives the motor M based on the motor drive command given by the position detection unit 1.

The shunt resistor Rs is provided between the motor drive unit 2 and the motor M, with one end connected to terminal T2 of the motor M and the other end connected to the motor drive unit 2. In a steady state in which the motor M is driven, a motor current Ia (drive current) as indicated by the thick arrow flows through the shunt resistor Rs. In addition, when the motor drive unit 2 shorts terminals T1 and T2 and brakes the motor M, or in a transient state in which the motor M rotates due to reaction force or inertia when the motor M is not driven, a motor current Ib (brake current) as indicated by the dotted arrow flows through the shunt resistor Rs. The directions of these currents are reversed.

The voltage detection unit 3 detects the voltage between terminals T1 and T2, and outputs the voltage value to the position detection unit 1 as the motor voltage V. The current detection unit 4 is connected to both ends of the shunt resistor Rs, detects the motor current based on the voltage drop that occurs across the shunt resistor Rs, and outputs the current value to the position detection unit 1 as the motor current I.

The ripple detection unit 5 is provided on the output side of the current detection unit 4, detects the ripple (pulsation) contained in the motor current detected by the current detection unit 4, and outputs the amplitude value as the ripple current Ir to the position detection unit 1.

The position detection unit 1 calculates the amount of rotation of the motor M based on the motor voltage V detected by the voltage detection unit 3, the motor current I detected by the current detection unit 4, and the ripple current Ir detected by the ripple detection unit 5, and detects the position of the electric seat 30, which is a moving body, based on the amount of rotation.

Figure 2 is a block diagram showing a specific configuration of the position detection unit 1. The position detection unit 1 has a first detection unit 1A and a second detection unit 1B. The first detection unit 1A has a ripple extraction filter 11, a binarization circuit 12, a position calculation unit 13, a fast Fourier transform circuit 14, a ripple frequency calculation unit 15, and a ripple frequency estimation unit 16. The second detection unit 1B has a motor rotation amount calculation unit 17 and a position calculation unit 18. The first detection unit 1A corresponds to the "first position detection unit" in this invention, and the second detection unit 1B corresponds to the "second position detection unit" in this invention.

For the sake of convenience, in FIG. 2, the first detection unit 1A and the second detection unit 1B are shown as hardware blocks, but the functions of each block are actually realized by software. Of course, the first detection unit 1A and the second detection unit 1B may also be configured from hardware.

In the first detection unit 1A, the ripple extraction filter 11 is composed of a bandpass filter of FIR (Finite Impulse Response) type in this embodiment. This ripple extraction filter 11 removes noise from the ripple current Ir input from the ripple detection unit 5 in FIG. 1 and extracts ripples contained in a predetermined band. The binarization circuit 12 binarizes the extracted ripples to "0" and "1" using a predetermined threshold value and converts them into ripple pulses (see FIG. 3(c)). The position calculation unit 13 counts the number of rising and falling edges of the ripple pulses output from the binarization circuit 12 and calculates the amount of rotation of the motor M from the count value. Then, the position of the electric seat 30 is calculated from this amount of rotation and output as position information.

The fast Fourier transform circuit 14 analyzes the frequency of the ripple current Ir to create a frequency spectrum. The ripple frequency calculation unit 15 calculates the ripple frequency (calculated value) using a known method based on the motor voltage V input from the voltage detection unit 3 in FIG. 1, the motor current I input from the current detection unit 4, the resistance value Rm of the motor M, and the induced voltage constant Ke of the motor M. The resistance value Rm and the induced voltage constant Ke are stored in a memory (not shown). The resistance value Rm and the induced voltage constant Ke may be periodically updated based on the motor voltage V and the motor current I. In this case, the parameters Rm and Ke are used as learning values, so that the ripple frequency can be calculated without being affected by variations in the characteristics of the motor M.

The ripple frequency estimation unit 16 estimates the ripple frequency using a known method based on the frequency spectrum created by the fast Fourier transform circuit 14 and the ripple frequency (calculated value) calculated by the ripple frequency calculation unit 15, and provides the estimated ripple frequency value to the ripple extraction filter 11. This causes the frequency characteristics of the ripple extraction filter 11 to be updated according to the ripple frequency, making it possible to extract a ripple in a specified band from the ripple current regardless of speed fluctuations of the motor M.

Next, the second detection unit 1B includes a motor rotation amount calculation unit 17 that calculates the amount of rotation of the motor M based on a predetermined calculation formula, and a position calculation unit 18 that calculates the position of the electric seat 30 based on the amount of rotation of the motor M calculated by the motor rotation amount calculation unit 17.

ここで、右辺のＶ－Ｒｍ・Ｉ／Ｋｅは、モータＭの速度（計算値）であり、これを時間積分することで、モータの回転量Ｐが算出される。位置算出部１８は、この回転量Ｐに基づいて電動シート３０の位置を算出し、これを位置情報として出力する。 The motor rotation amount calculation unit 17 calculates the motor rotation amount P using the motor voltage V, the motor current I, the resistance value Rm of the motor M, and the induced voltage constant Ke of the motor M according to the following equation.

Here, V-Rm·I/Ke on the right side is the speed (calculated value) of the motor M, and this is integrated over time to calculate the amount of motor rotation P. The position calculation unit 18 calculates the position of the electric seat 30 based on the amount of rotation P, and outputs this as position information.

Figure 3 shows the waveforms of the motor current, ripple current, and ripple pulse during the normal driving state of motor M, that is, during the period X from time t1, when a certain amount of time has elapsed since motor M was started, to time t2, when control to stop motor M is initiated. As can be seen from Figure 3, during period X, each waveform shows a steady change. This period X corresponds to the "first movement period" in the present invention, and during this period, the electric seat 30 continues to move due to the rotation of motor M.

During the above-mentioned period X, as shown by the bold frame in FIG. 4, the position of the electric seat 30 is detected only by the first detection unit 1A, and the second detection unit 1B shown by the dashed line is not involved in detecting the seat position. Therefore, in the normal state, the first detection unit 1A detects the position of the electric seat 30 in the same manner as in the conventional case.

Next, we will explain position detection when the motor current shows a transient change.

Figure 5 shows how a reaction force acts when the electric seat 30 is stopped. When the position detection unit 1 outputs a motor stop command to the motor drive unit 2 based on the seat position detection result (position information), the motor drive unit 2 shorts terminals T1 and T2 of the motor M. This applies a brake to the motor M, so that the moving electric seat 30 hits the stopper 31 and attempts to stop, but receives a reaction force from the stopper 31 and moves slightly backward in the opposite direction to the direction of movement. As a result, the motor M rotates in the opposite direction in association with the backward movement of the electric seat 30.

Figure 6 shows how the motor voltage and motor current change when the motor M rotates in reverse. t3 is the time when the electric seat 30 hits the stopper 31, and from this point on, a reaction force acts on the electric seat 30, causing the motor M to rotate in reverse and stop at t4. The period Y from t3 to t4 corresponds to the "second movement period" in this invention, and during this time the electric seat 30 continues to move backwards.

During the above-mentioned period Y, the reverse rotation of motor M generates an induced voltage in the motor windings, and based on this induced voltage, a motor current (brake current Ib in Figure 1) flows transiently through motor M. For this reason, the ripple current contained in the motor current exhibits a transient change. However, since the motor current at this time is very small, the amplitude of the ripple current contained in the motor current is extremely small and the waveform is also distorted. Therefore, this ripple current cannot be used to calculate the amount of reverse rotation of motor M.

In the present invention, in the period Y, as shown by the thick frame in FIG. 7, the position of the electric seat 30 is detected by the second detection unit 1B, and the seat position is not detected by the first detection unit 1A shown by the dashed line. Therefore, even without using a ripple current, the rotation amount P of the motor M can be calculated by the above-mentioned calculation formula (1) using the motor voltage (induced voltage) V detected by the voltage detection unit 3, the motor current (brake current) I detected by the current detection unit 4, the resistance value Rm of the motor M, and the induced voltage constant Ke of the motor M, and the position of the electric seat 30 can be detected from this rotation amount P. As a result, the reliability of the position detection is improved, and the position deviation (reverse rotation) of the electric seat 30 caused by the reaction force can be corrected based on the reverse rotation amount of the motor M.

In the above embodiment, a reaction force acts on the electric seat 30, but the present invention is also effective in cases where the electric seat 30 passes the stop position and stops (overruns) due to inertia, as shown in FIG. 8.

Figure 9 shows the changes in motor current and ripple current in this case. After the motor drive command is turned from ON to OFF, the motor M continues to rotate due to the overrun of the electric seat 30 from time t5 to time t6, and stops at time t6. The period Z from t5 to t6 corresponds to the "second movement period" in the present invention, during which the motor M transiently flows with a motor current (brake current Ib in Figure 1) based on the induced voltage generated in the motor winding. For this reason, the ripple current contained in the motor current also shows a transient change, but in this case too, the ripple current has a small amplitude and a distorted waveform. Therefore, the first detection unit 1A cannot calculate the motor rotation amount using this ripple current, but the second detection unit 1B can calculate the motor rotation amount using the above-mentioned calculation formula (1), making it possible to detect the position of the electric seat 30.

In the above-described embodiment, position detection is performed only by the first detection unit 1A during period X, and only by the second detection unit 1B during periods Y and Z. However, both the first detection unit 1A and the second detection unit 1B may continue position detection in parallel at all times, and the detection output may be switched between period X and periods Y and Z. That is, in the present invention, the position detected by the first detection unit 1A may be output during period X, when the ripple current shows a steady change, and the position detected by the second detection unit 1B may be output during periods Y and Z, when the ripple current shows a transient change.

In the above-described embodiment, the electric seat 30 of a vehicle is given as an example of a moving object, but the present invention can also be applied to detecting the position of moving objects such as vehicle windows, sliding doors, and sunroofs. The present invention can also be applied to detecting the position of moving objects used in fields other than vehicles.

Furthermore, in the above-mentioned embodiment, a position detection device 100 that detects the position of a moving body based on the amount of rotation of the motor M has been described, but the present invention can also be used as a rotation amount detection device that detects the amount of rotation of the motor M itself.

Fig. 10 shows an example of a motor rotation amount detection device 200 according to the present invention. The difference between Fig. 10 and Fig. 1 is that the position detection unit 1 for detecting the position of the moving body in Fig. 1 is replaced with a rotation amount detection unit 10 for detecting the amount of rotation of the motor. As the rest is the same as Fig. 1, the same reference numerals are used for the same parts as Fig. 1, and duplicated explanations will be omitted.

Fig. 11 is a block diagram showing a specific configuration of the rotation amount detection unit 10. In Fig. 11 , the difference from Fig. 2 is that the position calculation unit 13 in Fig. 2 is replaced with a motor rotation amount calculation unit 23, the position calculation unit 18 in Fig. 2 is omitted, and the first detection unit 1A in Fig. 2 is replaced with a first detection unit 10A, and the second detection unit 1B in Fig. 2 is replaced with a second detection unit 10B. Since the rest is the same as Fig. 2, the same parts as Fig. 2 are denoted with the same reference numerals and repeated explanations will be omitted.

The operation of the rotation amount detection unit 10 in FIG . 11 is basically the same as the operation of the position detection unit 1 in FIG. 2, except that the detection target is the rotation amount of the motor M. That is, the first detection unit 10A detects the rotation amount of the motor M from the ripple pulse based on the ripple current Ir. The second detection unit 10B detects the rotation amount of the motor M by calculation based on the above-mentioned formula (1) using the motor current I, the motor voltage V, the resistance value Rm of the motor M, and the induced voltage constant Ke of the motor M. Then, during a period (first period) in which the ripple current shows a steady change, the first detection unit 10A (first rotation amount detection unit) outputs the rotation amount detected, and during a period (second period) in which the ripple current shows a transient change, the second detection unit 10B (second rotation amount detection unit) outputs the rotation amount detected.

The motor rotation amount detection device 200 described above can be used not only to detect the position of a moving body such as an electric seat 30, but also to detect the amount of rotation and the rotation angle of a rotating body rotated by a motor M.

1 Position detection unit 1A First detection unit (first position detection unit)
1B Second detection unit (second position detection unit)
2 Motor drive unit 3 Voltage detection unit 4 Current detection unit 5 Ripple detection unit 10 Rotation amount detection unit 10A First detection unit (first rotation amount detection unit)
10B Second detection unit (second rotation amount detection unit)
REFERENCE SIGNS LIST 11 Ripple extraction filter 12 Binarization circuit 13 Position calculation section 14 Fast Fourier transform circuit 15 Ripple frequency calculation section 16 Ripple frequency estimation section 17 Motor rotation amount calculation section 18 Position calculation section 23 Motor rotation amount calculation section 30 Electric seat (mobile body)
100: Position detection device for a moving object 200: Motor rotation amount detection device M: Motor Rs: Shunt resistor T1, T2: Motor terminals X: First movement period Y, Z: Second movement period

Claims (4)

a motor driving unit that drives a motor for moving the moving body;
a voltage detection unit that detects a motor voltage, which is a voltage between terminals of the motor;
a current detection unit that detects a motor current flowing through the motor;
a ripple detection unit that detects a ripple current included in the motor current;
a first position detection unit that calculates a rotation amount of the motor based on the ripple current and detects a position of the moving body based on the rotation amount;
a second position detection unit that calculates an amount of rotation of the motor based on a predetermined equation using the motor voltage and the motor current, and detects a position of the moving body based on the amount of rotation,
In a first moving period of the moving object in which the ripple current shows a steady change, a position of the moving object detected by the first position detection unit is output;
a second movement period of the moving object in which the ripple current exhibits a transient change, the second position detection unit detects a position of the moving object, and outputs the position of the moving object detected by the second position detection unit;
a shunt resistor for detecting the motor current by the current detection unit;
a rotation of the motor during the second movement period causes an induced voltage to be generated between terminals of the motor and a brake current to flow through the shunt resistor;
a second position detection unit that detects a position of the moving body based on the amount of rotation of the motor using the induced voltage as the motor voltage and the brake current as the motor current, and detects the position of the moving body based on the amount of rotation . 2. The position detection device for a moving body according to claim 1 ,
The position detection device for a moving body, wherein the second movement period is a period during which the moving body moves in a direction opposite to the moving direction due to a reaction force after colliding with a stopper. 2. The position detection device for a moving body according to claim 1 ,
2. A position detection device for a moving body, wherein the second movement period is a period until the moving body passes a stop position due to inertia and stops. a motor driving unit that drives the motor;
a voltage detection unit that detects a motor voltage, which is a voltage between terminals of the motor;
a current detection unit that detects a motor current flowing through the motor;
a ripple detection unit that detects a ripple current included in the motor current;
a first rotation amount detection unit that detects a rotation amount of the motor based on the ripple current;
a second rotation amount detection unit that detects an amount of rotation of the motor based on a predetermined calculation formula using the motor voltage and the motor current,
In a first period in which the ripple current shows a steady change, the rotation amount detected by the first rotation amount detection unit is output,
a second rotation amount detection unit detecting a rotation amount of a motor during a second period in which the ripple current exhibits a transitional change, the second rotation amount detection unit detecting a rotation amount of a motor being outputted,
a shunt resistor for detecting the motor current by the current detection unit;
due to the rotation of the motor in the second period, an induced voltage is generated between terminals of the motor and a brake current flows through the shunt resistor,
a second rotation amount detection unit that detects an amount of rotation of the motor by using the induced voltage as the motor voltage and the brake current as the motor current ,

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