JP2005041352A - Torque controlling method for power-assisted bicycle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a torque controlling method for a power-assisted bicycle capable of determining whether zero point abnormality is due to some fault in a torque sensor itself or abnormal measuring operation when the zero point abnormality occurs. <P>SOLUTION: In this torque controlling method for the power-assisted bicycle comprising: a torque sensor 41 for detecting a stepping force from a pedal; a motor 42 for assisting the stepping force; a toque-current calculating means 50 for calculating a motor driving current instruction value based on the detection data of stepping force torque synchronously fluctuating with pedal rotation; and a motor driving circuit 44 for driving the motor based on the current instruction value, the toque-current calculating means measures the zero point of the torque sensor when the motor starts drive control, and subtracts a zero point value from the detection data of the torque sensor so as to calculate the stepping force. A torque sensor abnormality determination means 52 is provided, which sets a threshold for determining the torque sensor abnormality, judges abnormality to stop the motor driving when a state in which the lowest point of the detection data is larger than the threshold continues over a specified time. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a torque control method for a battery-assisted bicycle using a torque sensor that detects pedal effort.

A battery-assisted bicycle is disclosed in Patent Document 1. In this battery-assisted bicycle, a pedaling force depressed by a pedal is detected by a torque sensor, and auxiliary power corresponding to the pedaling force is applied from a motor. When calculating the drive current of this motor, first, when turning on the power and starting assist control by the motor, the torque value (zero point) of the torque sensor in the no-pressing force state is measured. Subsequently, the detection data of the pedaling force torque that fluctuates by repeating the uppermost point and the lowermost point in synchronization with the pedal rotation is read, and the pedaling force is calculated by subtracting the zero point value from the torque detection data value. A drive current command value for the motor is calculated based on the pedal effort. The motor rotates based on the current command value and assists the pedal effort.

However, when the zero point of the torque sensor is detected, a normal zero point may not be measured due to the following reasons.
1) Torque sensor failure 2) State in which pedal force was applied to the pedal during zero point measurement

The above 1 is a state where the torque sensor itself is abnormal and a correct zero point torque value in a no-load state cannot be measured. On the other hand, the above 2 is a state in which the zero point measurement value is abnormal because the zero point is measured in a state where the torque sensor itself is normal but the pedal is applied. Due to such a zero point abnormality, for example, when a high zero point torque is measured by a normal torque sensor, the zero point value is subtracted from the subsequent torque detection value. Assist power cannot be obtained. In addition, if an abnormality that increases the zero point measurement value occurs, and if the zero point value is set by lowering by a predetermined amount, then the pedaling force calculated from the torque detection value based on this zero point setting value is reduced. There is a possibility that an excessive assist force is applied from the motor due to the excessive increase.

  On the other hand, if it is determined that the torque sensor has failed evenly when a zero point abnormality occurs and the assist motor is stopped, the torque sensor will be activated when the zero point measurement operation is not normal with the normal torque sensor as described above. Despite functioning normally, the assist function cannot be obtained, and the original function of the battery-assisted bicycle becomes useless.

Japanese Patent Laid-Open No. 11-171081

  The present invention is based on the above prior art, and when a zero point abnormality occurs, it is determined whether the cause is a failure of the torque sensor itself or an abnormal measurement operation with a normal torque sensor, An object of the present invention is to provide a torque control method for a battery-assisted bicycle that can effectively perform a sensor function and perform highly reliable assist motor drive control.

  In order to achieve the above object, according to the first aspect of the present invention, a torque sensor for detecting the pedaling force from the pedal, a motor for assisting the pedaling force, and the highest point and the lowest point in synchronization with the pedal rotation detected by the torque sensor. Torque-current calculation means for calculating a drive current command value for the motor based on detection data of pedaling torque that fluctuates repeatedly, and the motor is driven based on a current command value from the torque-current calculation means. A motor drive circuit, and the torque-current calculation means measures the zero point of the torque sensor at the start of the drive control of the motor, and then subtracts the zero point value from the detection data of the torque sensor to calculate the pedaling force. In the torque control method for a battery-assisted bicycle, a threshold value for determining abnormality of the torque sensor is set, and a value of the lowest point of the detection data is the threshold value. Large state provides a torque control method of the motor-assisted bicycle, characterized in that to stop the drive determines that abnormality of the torque sensor of the motor when the subsequent predetermined time or more Ri.

The invention according to claim 2 is characterized in that the threshold value is changed based on the amplitude between the highest point and the lowest point of the detection data detected continuously.

The invention according to claim 3 is characterized in that the predetermined time is changed based on the vehicle speed.

The invention according to claim 4 is characterized in that the driving of the motor is not stopped when the amplitude between the uppermost point and the lowermost point of the detection data detected continuously is a predetermined value or more. .

According to the first aspect of the present invention, when the power supply is turned on and the drive control of the assist motor is started, when the zero point measurement value shows an abnormal value, a threshold value lower than the abnormal value is set. The failure of the torque sensor can be determined based on whether the lowest point of the detection data from the torque sensor thereafter falls below the threshold value within a predetermined time. In other words, if the torque sensor is normal, even if the zero point value is abnormal in the abnormal detection operation state where the pedal is pressed during zero point measurement, the normal point will cause the zero point to reach an output value close to zero. Since it falls, it falls below the set threshold value. On the other hand, when an abnormality occurs in the zero point value due to a failure of the torque sensor itself, the abnormal zero point is continuously output and does not fall below the threshold value. As a result, when a zero point abnormality occurs, it can be determined whether the torque sensor itself is faulty or whether the torque sensor is normal and only the measured value is abnormal. High assist motor drive control is possible.

  According to the second aspect of the present invention, the threshold of the torque sensor failure determination at the time of the zero point abnormality is changed according to the fluctuation range (amplitude) between the highest point and the lowest point of the torque fluctuation. Regardless, the torque sensor abnormality can always be accurately determined. That is, the lowest point of torque fluctuation is basically lowered to the zero point, but when the pedal effort is increased, the lowest point of torque fluctuation becomes higher. Accordingly, when the torque amplitude is large, the reliability of the torque sensor abnormality determination is improved by increasing the threshold value.

  According to the invention of claim 3, since the abnormality determination time of the torque sensor is changed according to the vehicle speed, the abnormality determination of the torque sensor can always be accurately performed regardless of the vehicle speed. In other words, the time of one cycle of the torque fluctuation waveform varies depending on the vehicle speed, and the faster the vehicle speed, the shorter the time of one cycle. Therefore, when the vehicle speed is high, the abnormality determination time can be shortened to determine the abnormality of the torque sensor in a short time. Thereby, when the vehicle speed is high, abnormality of the torque sensor can be detected quickly, and improper motor drive control using the abnormal torque sensor can be stopped immediately. In this case, even if the abnormality determination time is shortened, since the cycle of the torque fluctuation waveform is short and many bottom points can be detected in a short time, the determination accuracy is not lowered and the reliability of the determination is maintained.

  According to the fourth aspect of the present invention, for example, when the torque sensor is determined to be abnormal while a large pedaling force is applied on an uphill or the like, the assist by the motor can be continued without stopping. Thereby, for example, in the state where assistance such as uphill is necessary, the assist power from the motor can be obtained with certainty.

For example, as a first method, when a torque sensor is determined to be abnormal, a torque amplitude threshold value indicating whether or not to interrupt the drive current output to the motor is provided. If the torque amplitude is larger than the predetermined value when the zero point is abnormal, the torque sensor is abnormal or normal without performing abnormality determination of the torque sensor. Regardless of the method, it can be executed by the method of continuing the assist by the motor.

FIG. 1 is a side view of a battery-assisted bicycle to which the present invention is applied.
The battery-assisted bicycle 1 has a head pipe 4 through which the center steering shaft 3 of the left and right handles 2 is inserted, and the steering shaft 3 is connected to the left and right front forks 5 to operate the direction of the front wheels 6. A down tube 7 is joined to the head pipe 4 and connected to a seat tube 9 below the saddle 8. A power unit 11 in which an electric drive system such as a traveling electric motor 37 covered with a cover 10 and a human power drive system such as a pedal crankshaft are integrated at the lower ends of the down tube 7 and the seat tube 9 is supported. The In the power unit 11, the pedal force from the pedal 15 and the motor force are fused by a resultant force mechanism (not shown) arranged coaxially with the pedal crankshaft 12. The resultant force mechanism includes a planetary gear mechanism, and is provided with a pedaling force detection mechanism (torque sensor) that is connected to the planetary gear mechanism and is displaced according to the pedaling force from the pedal 15.

  An auxiliary power control controller 13 is provided at the rear of the power unit 11. The controller 13 is constituted by a microcomputer for driving and controlling the motor 37 so as to obtain an assist ratio corresponding to the speed based on the vehicle speed obtained by a vehicle speed calculating means (FIG. 2) described later. Such an installation position of the controller 13 is not limited to the example shown in the figure, and may be any appropriate position in the middle of the down tube 7 or in the cover 10, in the middle of the front fork 5, the chain stay 38, and the seat stay 39. Good.

  A battery case 14 is detachably provided on the rear side of the seat tube 9 below the saddle 8, and a battery for driving the motor 37 is accommodated therein. The pedaling force and auxiliary power fused by the resultant force mechanism on the pedal crankshaft 12 are transmitted to the rear wheel 17 by the chain 16 to rotate. The hub 18 of the rear wheel 17 is provided with a sprocket (not shown) for transmitting the rotation of the chain 16 and a rotary or slide type transmission gear mechanism (not shown). An actuator composed of a motor or a solenoid for driving the mechanism is mounted.

  FIG. 2 is a block diagram of the torque control device for the battery-assisted bicycle according to the embodiment of the present invention.

  The torque control device includes a torque sensor 41 for detecting pedal depression force, a controller 43 for calculating a drive current of an electric motor 42 composed of a pulse motor based on the detected torque of the torque sensor 41, and driving and controlling the drive current. A motor drive circuit 44 for driving the electric motor 42 by a drive signal from the controller 43, a current detection circuit (ammeter) 45 for detecting the current of the motor 42, and a rotation for detecting the rotation of the motor 42 And an encoder 46.

  The controller 43 is composed of, for example, a CPU, and includes a motor speed calculation means 47, a vehicle speed calculation means 48, a torque sensor value processing means 49, a torque-current calculation means 50, a duty calculation means 51 by a preset software program or hardware circuit. Is provided.

  The pedal depression force detected by the torque sensor 41 is noise-removed by the torque sensor value processing filter 49 and is calculated and processed based on the detected torque and the vehicle speed, and an output voltage (processing torque value) corresponding to the pedal depression force is obtained. can get. The vehicle speed is calculated by the motor speed calculation means 47 and the vehicle speed calculation means 48 in the controller 43 based on the pulse signal from the encoder 46 and is input to the processing filter means 49.

  The machining torque value after machining is input to the torque-current calculation means 50, and a current command value corresponding to the machining torque is calculated. Based on this current command value, the duty ratio of the drive pulse is calculated by the duty calculation means 51 and is input to the motor drive circuit 44 as a PWM output to drive the motor 42. The drive current of the motor 42 is detected by the current detection circuit 45 and returned to the duty calculation circuit 51 for feedback control.

  In this embodiment, based on the processing torque value obtained by processing the torque detection value from the torque sensor 1, as described later (FIG. 5), the torque that determines abnormality of the torque sensor and interrupts the assist when the sensor is faulty. Sensor abnormality determination means 52 is provided.

  FIG. 3 is a graph of a torque waveform showing torque fluctuation of torque detection data from the torque sensor. The horizontal axis represents time, and the vertical axis represents the detected torque value. a is an output waveform of the normal torque sensor, b is an output waveform of the abnormal torque sensor, and c is an output waveform of the normal torque sensor measured at a zero point in a state where the pedal force is applied. A indicates the zero point of the normal torque sensor, and B indicates the zero point of the abnormal torque sensor. Time t0 is the zero point measurement time when the power is turned on and the assist control is started. The pedal is depressed from time t1 to start traveling. Each of the graphs a, b, and c is a waveform that repeats the highest point (upper peak) and the lowest point (lower peak), and the width (torque amplitude) between successive highest points and lowest points is the pedal depression force. Corresponds to strength.

  In the case of a normal torque sensor, as shown in the graph a, the lowest point is always lowered to near the zero point A.

In the case of an abnormal torque sensor, as shown in the graph b, the lowest point is always lowered to near the zero point B higher than the zero point A.

  On the other hand, when the pedal is depressed for the zero point measurement time t0 with the normal torque sensor, as shown in the graph c, the detected torque value at the zero point measurement time t0 is larger than the original zero point A by the pedal depression force. Get higher. However, since the torque sensor itself is normal, during the subsequent running, the lowest point of the torque detection waveform decreases and approaches the normal zero point A.

  The present invention utilizes such torque detection data characteristics. As shown in the graphs b and c, the zero point is larger than the original A point when the zero point is measured (time t0) at the start of the assist control. When the number of points is exceeded, it is determined whether the torque sensor itself is abnormal (graph b) or whether the torque sensor is normal and the zero point measurement state is abnormal (graph c).

  As a determination method, a threshold value C is set at an intermediate point between the zero point A and the zero point B, and when the lowest point of the waveform of the torque detection data after the time point t1 falls below the threshold value C, it is normal. It is determined that the torque sensor is a correct torque sensor (graph c). In the example in the figure, the lowest point is lower than the threshold value C at time t3. When the time point t3 is obtained within a predetermined time from the start of assist control after turning on the power or from the time point t1 after the zero point measurement, it is determined that the torque sensor is normal (graph c). In the detected waveform when the torque sensor itself is abnormal (graph b), the lowest point is always equal to or higher than the zero point B and does not fall below the threshold value C.

  In the present invention, a threshold for torque sensor determination is further set according to the width (torque amplitude) between the highest point and the lowest point of the torque detection data waveform. This is because the lowest point changes in accordance with the torque amplitude in the case of a normal torque sensor. That is, when the torque amplitude is large (the pedal force is strong), the lowest point of the torque detection waveform becomes high. Therefore, when the torque amplitude is large, the abnormality of the torque sensor can be quickly and reliably determined by setting the threshold value high. In the example of the figure, if the threshold value is set at a point D that is somewhat higher than the point C, for example, according to the torque amplitude between the uppermost point and the lowermost point after the time point t1, the lowest point of the graph c at the time point t2 is the threshold value D. Therefore, it can be determined that the torque sensor is normal at this time t2.

  In the present invention, the abnormality determination time of the torque sensor is further changed according to the vehicle speed. By this, it becomes possible to always correctly determine the abnormality of the torque sensor regardless of the vehicle speed. In other words, the time of one cycle of the torque fluctuation waveform varies depending on the vehicle speed, and the faster the vehicle speed, the shorter the time of one cycle. Therefore, when the vehicle speed is high, the abnormality determination time can be shortened to determine the abnormality of the torque sensor in a short time. Thereby, when the vehicle speed is high, abnormality of the torque sensor can be detected quickly, and improper motor drive control using the abnormal torque sensor can be stopped immediately. In this case, even if the abnormality determination time is shortened, since the cycle of the torque fluctuation waveform is short and many bottom points can be detected in a short time, the determination accuracy is not lowered and the reliability of the determination is maintained.

  FIG. 4 is a graph showing the relationship between the torque amplitude and the abnormality determination threshold value of the torque sensor. The lowest point of torque fluctuation increases as the torque amplitude increases. Therefore, the abnormality determination threshold value (C, D in FIG. 3) of the torque sensor is increased as indicated by a graph (broken line) d corresponding to this lowest point. An upper area E of the threshold graph d is a torque sensor abnormality determination area (an area where the lowermost point is not lowered to the threshold d), and an area F below the graph d is a torque sensor normal determination area (the lowermost point is a threshold). d) or less).

  The normality / abnormality of the torque sensor is determined by setting the threshold value, and when the torque sensor is abnormal, the assist of the motor is interrupted as will be described later (FIG. 5). In the present invention, this assist interruption is performed only when the torque amplitude is equal to or smaller than the predetermined value Tw. That is, in the region where the torque amplitude in FIG. 4 is equal to or less than Tw, the assist continues without interruption regardless of whether the torque sensor is abnormal (E region) or normal (F region). Thereby, for example, in the state where assistance such as uphill is necessary, the assist power from the motor can be obtained with certainty.

As a method for determining such assist interruption, for example, as a first method, when it is determined that the torque sensor is abnormal, torque for determining whether or not to interrupt the drive current output to the motor as shown in FIG. A method of setting an amplitude threshold Tw so that the motor drive is not stopped when the torque amplitude is greater than or equal to the threshold Tw, or as a second method, when the torque amplitude is larger than a predetermined value when the zero point is abnormal Can be executed by a method of continuing assist by the motor regardless of whether the torque sensor is abnormal or normal without performing abnormality determination of the torque sensor.

  FIG. 5 is a flowchart showing a procedure of an assist control program by the electric motor according to the embodiment of the present invention. The routine of each step is as follows. This program control is performed by the torque sensor abnormality determination means 52 of FIG.

Step S1:
After processing the output value from the torque sensor into a voltage output that can be processed through a filter, the values of the highest point (top peak) and the lowest point (bottom peak) of this detected torque waveform data (see Fig. 3) Is read.

Step S2:
Determine whether in assist mode. If it is not the assist mode, the process exits from the flow and ends without executing the following processing.

Step S3:
In the assist mode, the torque amplitude (uppermost point-lowermost point) is calculated from the data in step S1.

Step S4:
A threshold (bottom voltage threshold) at the lowest point of the torque detection data is calculated from the torque amplitude. This is a step for carrying out the invention of claim 2. As described above, when an abnormality occurs in the zero point measurement value, the torque sensor itself is abnormal or the torque sensor is normal and the measurement state is A threshold for determining whether a zero point abnormality has occurred due to an abnormality (Claim 1), and the threshold is set corresponding to the torque amplitude.

Step S5:
It is determined whether the lowest point voltage of the torque detection data is lower than the threshold value in step S4. This is a step for carrying out the invention of claim 1. If the bottom voltage of the torque voltage data becomes lower than the threshold value, it can be determined as a normal torque sensor, and the counter for counting the abnormality determination time is cleared.

Step S6:
The torque sensor abnormality determination counter is cleared and the flow ends. This is a case where the determination result is normal.

Step S7:
It is determined whether or not the torque amplitude is equal to or less than a predetermined amplitude that allows the assist stop. This is a step corresponding to the invention of claim 4, and is a step for determining whether or not the assist can be stopped immediately when there is an abnormality in the zero point measurement value. If the torque amplitude is equal to or smaller than the predetermined value, the assist can be stopped, and the process proceeds to the assist stop process in step S9 and subsequent steps. If the torque amplitude is larger than the predetermined value, the assist cannot be stopped regardless of whether the torque sensor is normal or abnormal (for example, uphill). Therefore, the torque sensor abnormality determination counter is cleared (step S8), and the torque sensor abnormality determination is performed. The flow is terminated without performing.

Step S8:
The torque sensor abnormality determination counter is cleared and the flow ends. This ends the flow in order to avoid stopping the assist according to the determination result in a situation where the assist is required.

Step S9:
Based on the current vehicle speed calculated by the vehicle speed calculation means 8 (FIG. 2), the abnormality determination time of the torque sensor is set. This is a routine for carrying out the invention of claim 3. As described above, the time of one cycle of the torque fluctuation waveform varies depending on the vehicle speed, and the faster the vehicle speed, the shorter the time of one cycle. Therefore, when the vehicle speed is high, the abnormality determination time can be shortened to determine the abnormality of the torque sensor in a short time. Thereby, when the vehicle speed is high, abnormality of the torque sensor can be detected quickly, and improper motor drive control using the abnormal torque sensor can be stopped immediately. In this case, even if the abnormality determination time is shortened, since the cycle of the torque fluctuation waveform is short and many bottom points can be detected in a short time, the determination accuracy is not lowered and the reliability of the determination is maintained.

Step S10:
It is determined whether or not the torque sensor abnormality determination time calculated in step S9 has elapsed. If it has not elapsed, the flow is temporarily terminated. Here, the flow is temporarily exited, and the control program flow at the time of the zero point abnormality is repeated from START until the passage of time.

Step S11:
When the abnormality determination time of the torque sensor calculated in step S9 has elapsed, the assist interruption flag is set, the current command to the assist motor is stopped, and the motor drive is stopped. This is a situation where the counter is not cleared until the abnormality determination time elapses, and the state where the lowest point of the torque detection data is higher than the threshold value continues until the determination time elapses, and the torque sensor itself is determined to be abnormal. It is. In such a state, since there is a possibility that appropriate assist power corresponding to the pedal effort may not be applied, the assist is interrupted.

1 is an overall view of a battery-assisted bicycle to which the present invention is applied. The block diagram which shows the structure of embodiment of this invention. The graph which shows the waveform of the detection data from a torque sensor. Explanatory drawing of the threshold value of torque sensor abnormality determination. The flowchart which shows the procedure of embodiment of this invention.

Explanation of symbols

1: Electric assist bicycle, 2: Handle, 3: Steering shaft,
4: Head pipe, 5: Front fork, 6: Front wheel,
7: Down tube, 8: Saddle, 9: Seat tube, 10: Cover, 11: Power unit, 12: Pedal crankshaft, 13: Controller, 14: Battery case, 15: Pedal, 16: Chain, 17: Rear wheel 18: Hub, 37: Electric motor, 38: Chain stay,
39: Seat stay, 41: Torque sensor, 42: Electric motor,
43: Controller, 44: Motor drive circuit,
45: Current detection circuit (ammeter), 46: Encoder,
47: motor rotation speed calculation means, 48: vehicle speed calculation means,
49: Torque sensor value processing means, 50: Torque-current calculation means,
51: Duty calculation means, 52: Torque sensor abnormality determination means.

Claims (4)

A torque sensor that detects the pedaling force from the pedal;
A motor to assist the pedaling force;
Torque-current calculation means for calculating a drive current command value for the motor based on detection data of pedaling force torque that fluctuates by repeating the highest point and the lowest point in synchronization with the pedal rotation detected by the torque sensor;
A motor drive circuit for driving the motor based on a current command value from the torque-current calculation means,
The torque-current calculating means measures the zero point of the torque sensor at the start of driving control of the motor, and then subtracts the zero point value from the detection data of the torque sensor to calculate the pedaling force. In
A threshold for determining the abnormality of the torque sensor is set, and when the value of the lowest point of the detected data is greater than the threshold for a predetermined time or more, it is determined that the torque sensor is abnormal and the driving of the motor is stopped. A torque control method for a battery-assisted bicycle.   The torque control method for a battery-assisted bicycle according to claim 1, wherein the threshold value is changed based on an amplitude between the uppermost point and the lowermost point of the detection data that are continuously detected.   3. The torque control method for a battery-assisted bicycle according to claim 1, wherein the predetermined time is changed based on a vehicle speed. The drive of the motor is not stopped when the amplitude between the highest point and the lowest point of the detection data detected continuously is a predetermined value or more. Torque control method for battery-assisted bicycles.

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