JP2010158090A - Electric vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric vehicle wherein speed can be controlled with high response and following capability by directly determining an optimum torque command signal to be inputted to an in-wheel motor 9 from the running load of the electric vehicle as well as the difference between a target running speed and a detected running speed. <P>SOLUTION: An acceleration is determined from change in detected running speed by an acceleration acquisition means 15. The running load of the electric vehicle is determined from this acceleration and the output torque of the in-wheel motor 9 by a running load acquisition means 16. In correspondence with this running load, a torque command signal to be inputted to the in-wheel motor 9 is determined by a torque command signal control means 14 so as to produce an output torque for obtaining an acceleration with which the difference between the target running speed and the detected running speed is eliminated. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electric vehicle in which a driver indicates a target traveling speed by stepping on a pedal with his / her foot and rotating the pedal.

  Conventionally, an electric vehicle that detects the pedal rotation speed when the driver steps on the pedal and rotates the pedal and drives and controls the electric motor so as to travel at a speed corresponding to the pedal rotation speed has been developed. (For example, refer to Patent Document 1). Rotation angle when the handlebar's accelerator grip is held and turned, and stepping angle when the accelerator pedal on the floor is stepped on with a foot are detected, and the motor is driven to run at a speed corresponding to the turning angle and degree of depression. An electric vehicle that drives and controls a motor is also considered.

  Here, in a brushless DC motor often used in an electric vehicle such as an electric motorcycle, an output torque is increased in proportion to a value of a control voltage input as a torque command signal to a motor drive circuit that performs drive control of the motor. It is common to be controlled. When a control voltage corresponding to the rotation angle of the accelerator grip or the like is input to the motor drive circuit of the brushless DC motor as a torque command signal, the driver himself / herself adjusts the rotation angle of the accelerator grip and desires it. Control to run at speed.

  On the other hand, as described above, when the target traveling speed (target traveling speed) is instructed according to the rotation angle of the accelerator grip, the actual traveling speed of the electric vehicle matches the target traveling speed. Thus, it is necessary to separately provide a torque command signal control means for controlling a control voltage which is a torque command signal, and to control the speed of the brushless DC motor by this torque command signal control means.

  As a method for controlling the speed of such an electric motor, a method is considered in which the control voltage, which is a torque command signal of the brushless DC motor, is increased or decreased at a certain rate. The brushless DC motor has a maximum output torque when the control voltage is 4.1 V, and 0 when the control voltage is 1.1 V or less. According to this control method, when starting on a flat ground with a target travel speed of 6 km / h, as shown in FIG. 4, first, the control voltage of the electric motor is set to 3 V as an initial value, and this control voltage is set to Raise it at a certain rate. Then, after 1 second, since the traveling speed exceeds 4 km / h, the control voltage is decreased at a constant rate, but the acceleration continues and the traveling speed further increases. However, since the acceleration decreases due to a decrease in the control voltage, the running speed starts to decrease after 1.6 seconds. Therefore, if the control voltage is maintained at a level slightly higher than 1.1 V, the traveling speed is stabilized at about 6 km / h, and the constant speed traveling is performed.

  However, when starting on an uphill, as shown in FIG. 5, the running speed exceeds 4 km / h after 1.7 seconds by raising the control voltage of the electric motor from 3 V at a constant rate. When the control voltage is lowered at a certain rate, the traveling resistance due to the uphill is large, so that the traveling speed starts to decrease without reaching 5 km / h after a further increase, and again after 2.3 seconds, 4 km / h again. It will be slower. Therefore, the control voltage is increased again at a constant rate. However, since the rate of increase in the control voltage is small, the traveling speed further decreases and the vehicle stops.

  When the electric vehicle starts, a large acceleration is required and the control voltage is increased to increase the output torque. However, when the vehicle is on a flat ground, the output torque is hardly required when driving at a constant speed, so the control voltage must be lowered. However, when starting uphill, a large traveling load is applied to the electric vehicle. Therefore, it is necessary to increase the control voltage to some extent even during constant speed traveling to generate output torque. The case cannot be dealt with, and the electric vehicle stops.

  For this reason, if proportional control (P control in PID control) is performed to change the rate at which the control voltage of the electric motor is increased or decreased in proportion to the difference between the target travel speed and the actual travel speed, the travel load changes greatly. Even if the travel speed drops significantly, the difference between this travel speed and the target travel speed increases, so the rate of increase in the control voltage of the electric motor can be increased, and the electric vehicle stops on the uphill. There is nothing wrong.

  However, such proportional control alone does not provide sufficient response when the target travel speed is suddenly changed greatly, and followability with respect to large fluctuations in travel load. In addition, if the ratio (gain) of increasing the control voltage of the electric motor is further increased in order to improve the response and followability, the stability of the feedback control is deteriorated.

Therefore, it is conceivable to add differential control (D control in PID control) to the proportional control. In differential control, the temporal change of the difference between the target travel speed and the actual travel speed, that is, the acceleration when the travel speed approaches the target travel speed is detected. For example, when the travel speed is not close to the target travel speed, On the other hand, if you are going away, you can improve the response and follow-up performance by raising the control voltage even greater than the rate of increase of the control voltage due to the difference between the target travel speed and the travel speed at that time. it can. In addition, since integral control (I control in PID control) has little relation to responsiveness and follow-up performance, description thereof is omitted here.
JP-A-8-108881

  However, even in the case of PID control or the like in which differential control is added to the above proportional control, the control voltage of the electric motor is controlled based only on the difference between the target travel speed and the actual travel speed or the differential value (acceleration). Therefore, for example, the difference in travel load due to gentle slopes or steep slopes is not taken into account.For such travel load fluctuations, the actual travel speed does not readily follow the target travel speed, etc. Thus, there is a problem that the response and follow-up performance are not always sufficient since it cannot be dealt with until it is detected that the change in the differential value is insufficient. In addition, in order to perform such precise control, it is necessary to perform control at short time intervals, and a precise device is also required for detecting the actual traveling speed of the electric vehicle, which causes an increase in cost. There was also a problem.

  In other words, the actual traveling speed of the electric vehicle changes depending on the force obtained by subtracting the traveling load from the propulsive force generated by the output torque of the electric motor at that time, but conventionally, the magnitude of the traveling load is considered. Such a problem occurs because the control is performed only on the basis of the change in traveling speed.

  Specifically, the acceleration a of the electric vehicle has a relationship of a = F / m (F = ma), where m is the mass of the electric vehicle and F is the force applied to the electric vehicle. The force F applied to the electric vehicle is P, where the propulsive force of the electric vehicle by the output torque of the electric motor is P, and L is the driving load that is the force to pull back the electric vehicle (in the case of a downhill, the driving load L Is negative), and therefore, the acceleration a has a relationship of a = (P−L) / m. In addition, since the mass m of the electric vehicle is a constant during traveling, if the traveling load L is known, the propulsive force P can be determined according to how much acceleration a the electric vehicle requires. In other words, if it is known how much the electric vehicle should be accelerated, the optimum torque command signal (control voltage) of the electric motor that will be required in the future can be directly determined from the current running load. Is to change the torque command signal of the electric motor to some extent from the current state without considering the running load, detect the change (acceleration) of the running speed and determine whether to further change the torque command signal I was doing a round speed control.

  The present invention obtains the running load of the electric vehicle from the acceleration obtained from the running speed and the output torque of the electric motor, and directly determines the optimum torque command signal of the electric motor from the running load, thereby providing responsiveness and followability. It is an object of the present invention to provide an electric vehicle capable of performing high speed control.

  According to the first aspect of the present invention, in an electric vehicle driven by an electric motor in which a target traveling speed is instructed by a driver's operation and an output torque is controlled by a torque command signal, the traveling speed for detecting the traveling speed of the electric vehicle is detected. An electric vehicle based on a detection means, an acceleration acquisition means for obtaining an acceleration from a speed change per unit time of the detected travel speed detected by the travel speed detection means, an acceleration obtained by the acceleration acquisition means, and an output torque of the electric motor So as to generate the output torque for obtaining the acceleration that eliminates the difference between the target travel speed and the detected travel speed, corresponding to the travel load obtained by the travel load obtaining means. And torque command signal control means for determining a torque command signal to be input to the electric motor.

  The invention according to claim 2 is characterized in that the target travel speed is instructed according to a pedal rotation speed when the driver steps on the pedal with his / her foot to rotate the pedal.

  The invention of claim 3 is characterized in that the torque command signal is a control voltage.

  According to a fourth aspect of the present invention, the acceleration acquisition means, the travel load acquisition means, and the torque command signal control means determine the acceleration, the travel load, and the torque command signal, respectively, based on a table prepared in advance. It is characterized by that.

  According to the first aspect of the present invention, the traveling load acquisition means can determine the traveling load from the acceleration and the output torque. The torque command signal control means can determine what kind of acceleration is necessary for the electric vehicle in order to eliminate the difference between the target traveling speed and the detected traveling speed, and is optimal for obtaining such acceleration. A torque command signal for a simple electric motor can be determined in correspondence with the traveling load. Therefore, instead of adjusting the torque command signal of the electric motor so far, the torque command signal is determined directly from the traveling load received by the electric vehicle due to the hill or wind, etc. It becomes possible to perform speed control with extremely high responsiveness and followability to fluctuations in travel load.

  Here, the acceleration a, the propulsive force P, the traveling load L, and the mass m of the electric vehicle have a relationship of a = (P−L) / m. The torque command signal of the electric motor and the output torque generally have a specific relationship (proportional relationship, etc.), and the output torque and the propulsive force P of the electric vehicle also have a specific relationship (proportional relationship, etc.). If you know, other things are also uniquely determined. Further, the mass m of the electric vehicle is a constant during traveling because it is the mass of the electric vehicle plus the weight of the passenger and the weight of the load. Accordingly, the mass m of the electric vehicle can be set in advance by adding the standard weight of the person as the weight of the driver to the body mass of the electric vehicle, for example, or the setting can be changed as appropriate at the start of driving. If the vehicle is provided with a detector for measuring the mass of the passenger or the load, the detection value can be added to the vehicle body mass of the electric vehicle.

  As a result, the traveling load acquisition means can obtain the output torque and the propulsive force P from the current torque command signal of the electric motor, so the traveling load L is determined from the acceleration a obtained by the acceleration acquisition means and the propulsion force P. Can be sought. Further, the torque command signal control means is required from the acceleration a required for promptly matching the detected travel speed with the target travel speed and the current travel load L obtained by the travel load acquisition means. The propulsive force P can be determined, and a torque command signal can be obtained from the propulsive force P and input to the electric motor.

  The torque command signal for controlling the output torque of the electric motor is, for example, when the motor drive circuit of the brushless DC motor has a control voltage input terminal for controlling the output torque in addition to the drive power supply terminal. This corresponds to the control voltage input to the control voltage input terminal. In the case of a DC motor having a commutator, since there is a substantially proportional relationship between the voltage of the driving power and the output torque, the voltage of the driving power can be used as a torque command signal. When the motor drive circuit controls the voltage of the drive power supplied to the motor drive circuit, the control voltage for instructing the motor drive circuit to be controlled can be used as the torque command signal. Moreover, even in the case of a brushless DC motor, the motor drive circuit has only a drive power supply terminal, and the voltage of the drive power and the output torque are controlled so as to have a proportional relationship similar to that of the DC motor. This is the same as the case of this DC motor.

  Since the torque command signal may be a signal for controlling the output torque, the output torque is not limited to a voltage value such as a control voltage, but the output torque is controlled by, for example, the number of pulses or a digital value represented by the pulses. It may be a thing.

  The traveling load acquisition means may obtain the output torque of the electric motor from a torque detector that detects the actual output torque of the electric motor instead of from the torque command signal. For example, some brushless DC motor drive circuits detect and output such output torque. In particular, when there is a controllable correlation between the torque command signal of the electric motor and the output torque, but there is no specific relationship such that if one is known, the other is uniquely determined. Therefore, it is necessary to use the output torque detected by such a torque detector.

  According to the invention of claim 2, since it is necessary to rotate the pedal at a high speed in order to perform the maximum accelerator operation, it is possible to provide an electric vehicle that is easy to drive at an appropriate speed.

  According to the invention of claim 3, by using the control voltage as the torque command signal, the handling of the torque command signal is simple, easy to operate, and malfunction can be prevented.

  According to the fourth aspect of the present invention, the acceleration acquisition means, the running load acquisition means, and the torque command signal control means determine the corresponding acceleration, running load, and torque command signal based on a table prepared in advance. As a result, calculation processing is not required, and the processing can be realized using a processing device with low calculation capability. Further, for example, in the case of the torque command signal control means, the difference between the target travel speed and the detected travel speed is calculated when the target travel speed is greater than or equal to the detected travel speed and when the target travel speed is less than the detected travel speed. If it is divided into only two cases, the size (capacity) of the table can be reduced.

  Hereinafter, the best embodiment of the present invention will be described with reference to FIGS.

  In the present embodiment, an electric vehicle as shown in FIG. 1 will be described. This electric vehicle is a four-wheeled vehicle including a front wheel 1 as a steering wheel and a rear wheel 2 as a driving wheel, and a pair of auxiliary wheels 3 and 3 on the left and right of the rear wheel 2. . Each auxiliary wheel 3 is a driven wheel having a diameter slightly smaller than that of the rear wheel 2, and is attached so as to be movable up and down while being urged downward with respect to the frame of the electric vehicle.

  In this electric vehicle, the driver 6 steps the pedal 6 with his / her foot while rotating the front wheel 1 by straddling the saddle 4 and holding the handle 5 with both hands. However, this electric vehicle is not driven by transmitting the rotational force when the pedal 6 is squeezed to the rear wheel 2 like a bicycle or an electric power assisted bicycle, but by a storage battery 8 housed under the loading platform 7. The rear wheel 2 is driven by rotating an in-wheel motor 9 directly connected to the second axle. The pedal 6 detects the rotational speed when the pedal 6 is stepped on with a foot by the pedal rotational speed detector 10 and controls the speed of the in-wheel motor 9 according to the rotational speed detected by the pedal rotational speed detector 10. Is supposed to do.

  The in-wheel motor 9 is a brushless DC motor. The brushless DC motor eliminates the commutator (using the brush) of the DC motor (DC motor), detects the rotation angle of the rotor (rotor) with a Hall element, etc., and the direction of the coil current by the built-in motor drive circuit Is switched. In addition, the motor drive circuit of the brushless DC motor used here is supplied with drive power from the storage battery 8 and also receives a torque command signal, which will be described later, as a control voltage. Drive control is performed so as to obtain a proportional output torque. However, the relationship between the control voltage and the output torque is actually such that the output torque remains zero until the control voltage reaches a certain voltage value, and after this voltage value is exceeded, a linear relationship is established. is there. Note that some brushless DC motor drive circuits have a speed control function. However, since the speed control here is based on conventional PID control, such a brushless DC motor is used. There is no need.

  The rotational speed of the pedal 6 detected by the pedal rotational speed detector 10 is input to the target travel speed acquisition means 11 as shown in FIG. The pedal rotation speed detector 10 is a rotary encoder such as a magnetic system that detects the approach of each tooth of an iron gear with a magnetic sensor, or an optical system that detects transmitted light by applying light to a disk formed with a slit. It is possible to use a dynamo or the like that generates a voltage corresponding to the rotational speed.

  The target travel speed acquisition means 11 converts the rotational speed of the pedal 6 sent from the pedal rotational speed detector 10 into a target travel speed. Since the rotational speed of the pedal 6 indicates the target traveling speed of the electric vehicle by this, it is converted into the target traveling speed according to a predetermined rule (for example, proportional relationship). Therefore, the target travel speed acquisition means 11 can convert the rotational speed of the pedal 6 into the target travel speed by calculation of a calculation formula, conversion using a table, or the like.

  An electromagnetic pick that detects the rotation of the tire by detecting the unevenness of the magnetic material at the motor edge portion on the frame portion facing the circumferential edge portion of the motor case (hub portion) of the rear wheel 2 as the driving wheel. A rear wheel rotational speed detector 12, which is an up-type proximity sensor, is attached, and the rotational speed of the rear wheel 2 detected by the rear wheel rotational speed detector 12 is input to the detected traveling speed acquisition means 13. ing. As with the pedal rotation speed detector 10, the rear wheel rotation speed detector 12 is a rotary encoder attached to the axle of the rear wheel 2 (the rotation axis of the in-wheel motor 9) directly or via a transmission. Or dynamo can be used. If the motor drive circuit of the in-wheel motor 9 can output the rotation speed to the outside, the output of this rotation speed may be used instead of the rear wheel rotation speed detector 12.

  The detected traveling speed acquisition means 13 converts the rotational speed of the rear wheel 2 sent from the rear wheel rotational speed detector 12 into the detected traveling speed. The rotation of the rear wheel 2 detected by the rear wheel rotational speed detector 12 is obtained by multiplying the circumference of the tire of the rear wheel 2 by using the circumference of the diameter of the tire (in this embodiment, a tire having a diameter of 20 inches). If the speed is multiplied, the actual traveling speed of the electric vehicle can be calculated. Note that the circumferential length changes depending on the tire pressure of the rear wheel 2 and the like, and if the rear wheel 2 slips, the rotation is not related to the running speed. Appropriate correction may be performed when converting the detected traveling speed to the detected traveling speed. However, in this embodiment, instead of such calculation processing, the rotational speed of the rear wheel 2 is converted into the detected traveling speed using Table 1.

  This Table 1 is a correspondence table in which the “interval time” column and the “traveling speed” column are arranged on the left and right. In the “interval time” column, the interval time (unit: second) is set in order, and in the “running speed” column, the traveling speed (unit: km / h) corresponding to the interval time of the same row is set. ing. In addition, each interval time in the “interval time” column indicates a time exceeding the interval time one row below and below the interval time. However, the blank in the top row in the “Interval Time” column indicates all times exceeding the interval time one row below (0.2128 seconds in Table 1), and the interval time in the bottom row is the interval time (table 1 indicates all times less than or equal to 0.0266 seconds). In addition, here, for simplification of Table 1, rows are thinned out, but in the table actually used, the traveling speed in the column of “traveling speed” is 0 km / h to 25 km / h every 1 km / h. Is set in the steps.

  The rear wheel rotational speed detector 12 generates a pulse every time it approaches the unevenness of the magnetic material at the edge of the motor case (arranged at nine locations on the circumference at equal angular intervals). The generation interval time indicates the rotational speed of the rear wheel 2. Therefore, each time this pulse is sent, the detected travel speed acquisition means 13 measures the time from the previous pulse to the current pulse, and corresponds to the time measured from the “interval time” column in Table 1. In addition to searching for the interval time, the travel speed in the same row as the searched interval time in the “travel speed” column is read and output as the detected travel speed. When a pulse is sent for the first time from the rear wheel rotational speed detector 12, time cannot be measured, so the detected traveling speed is set to zero.

  The target travel speed converted by the target travel speed acquisition means 11 and the detected travel speed converted by the detected travel speed acquisition means 13 are input to the torque command signal control means 14. The torque command signal control means 14 determines a control voltage to be input to the in-wheel motor 9 as a torque command signal. Conventionally, the torque command signal control means 14 determines a control voltage as a torque command signal by, for example, PID control based on only the difference between the target travel speed and the detected travel speed. However, in the torque command signal control means 14 of the present embodiment, the acceleration that eliminates the difference between the target travel speed and the detected travel speed is obtained corresponding to the travel load obtained by the acceleration acquisition means 15 and the travel load acquisition means 16. A control voltage as a torque command signal is determined so that an output torque to be obtained is generated.

  For this reason, the detected travel speed converted by the detected travel speed acquisition means 13 is also input to the acceleration acquisition means 15. The acceleration output by the acceleration acquisition unit 15 is input to the traveling load acquisition unit 16. The traveling load acquisition means 16 is also supplied with a control voltage as a torque command signal output from the torque command signal control means 14.

  The acceleration acquisition means 15 obtains a speed change per unit time of the detected travel speed sent from the detected travel speed acquisition means 13, that is, an acceleration. The acceleration can be obtained by differentiating the detected traveling speed or by dividing the difference from the previous detected traveling speed by the sampling interval for each sampling in the digital system, but here the detected traveling speed is different at different time intervals. Since it is sent, it is necessary to divide the difference between the previous detected travel speed and the current detected travel speed by the time interval from the previous time to the current time. Therefore, in the present embodiment, the acceleration is obtained using Table 2.

This table 2 is a table in which interval times (unit: seconds) corresponding to each combination of the traveling speed (unit: km / h) of the header row and the acceleration (unit: m / s ² ) of the header column are arranged in a matrix. is there. Each travel speed in the heading row is the detected travel speed converted by the detected travel speed acquisition means 13 last time, and each interval time in the matrix is an interval time until the detected travel speed acquisition means 13 converts the current travel speed detected. is there. Then, in the row of each acceleration in the header column, an interval time indicating the time that will be required to convert the currently detected traveling speed when the previously detected traveling speed of each column is changed by the acceleration is set. Has been. Therefore, since the row where the acceleration is 0 indicates the case where the current detected traveling speed is the same as the previous time, it is the same as the case where the “interval time” column of Table 1 is changed to a row. Further, each interval time of the matrix indicates the time exceeding the interval time one row below and below the interval time, as in the case of Table 1. However, in this case as well, in order to simplify Table 2, rows and columns are thinned out, and the right column is partially omitted. In Table 2, only the positive acceleration when the electric vehicle accelerates is shown, but the same table is used for the negative acceleration in the case of deceleration.

  Each time the detected travel speed is sent from the detected travel speed acquisition means 13, the acceleration acquisition means 15 searches the detected travel speed sent last time from the travel speed in the heading row of Table 2 and An interval time corresponding to the time required between the previous time and this time (this time may be acquired from the detected traveling speed acquisition means 13 or may be measured again) is searched from the column, and the heading in the same row as this interval time is searched. Read the column acceleration and output it. When the detected travel speed is sent for the first time from the detected travel speed acquisition means 13, the previous detected travel speed does not exist, so the acceleration is set to zero.

  The traveling load acquisition means 16 obtains the traveling load based on the acceleration sent from the acceleration acquisition means 15 and the control voltage as the torque command signal sent from the torque command signal control means 14. . The acceleration a, the propulsive force P, the traveling load L, and the mass m of the electric vehicle have a relationship of a = (P−L) / m, and the propulsive force P is an output torque proportional to the control voltage of the in-wheel motor 9. In this embodiment, the mass m is a constant set in advance by adding the standard weight of a person to the vehicle body mass of the electric vehicle. Therefore, if the acceleration a and the control voltage are known, the running load L can be calculated. . However, in this embodiment, this traveling load is obtained using Table 3.

This Table 3 is a table in which travel loads (unit: N) corresponding to combinations of heading row acceleration (unit: m / s ² ) and heading column control voltage (unit: V) are arranged in a matrix. Here, however, rows and columns are thinned out in order to simplify Table 3. In Table 3, only positive acceleration is shown, but the same table is used for negative acceleration. In Table 3, only a positive travel load is set, but a negative travel load is actually set.

  Each time acceleration is sent from the acceleration acquisition means 15, the traveling load acquisition means 16 searches the acceleration and the control voltage at that time from the heading row and heading column in Table 3, and searches the acceleration column and search The driving load at the portion where the control voltage rows intersect is read and output.

  The torque command signal control means 14 also inputs the travel load obtained by the travel load acquisition means 16 together with the target travel speed converted by the target travel speed acquisition means 11 and the detected travel speed converted by the detected travel speed acquisition means 13. To do. Then, an acceleration necessary to quickly eliminate the difference between the target traveling speed and the detected traveling speed is obtained, and a control voltage necessary to obtain the acceleration under the current traveling load is determined. That is, as described above, the acceleration m, the propulsive force P, the traveling load L, and the constant mass m have a relationship of a = (P−L) / m. If it is known, the propulsive force P can be calculated, and a control voltage as a torque command signal can be obtained from the propulsive force P. However, in this embodiment, this control voltage is obtained using Table 4.

  This Table 4 is a correspondence table in which a column of “traveling load”, a column of “control voltage” at the time of acceleration, and a column of “control voltage” at the time of deceleration are arranged side by side. In the “running load” column, the running load (unit is N) is set in order, and in the “control voltage” column at the time of acceleration and deceleration, the torque command signal corresponding to the running load of the same row, respectively. A control voltage (unit: V) is set. Here, however, the lines are thinned out in order to simplify Table 4. In Table 4, only positive acceleration is shown, but the same table is used for negative acceleration. Also in Table 4, only a positive travel load is set, but a negative travel load is actually set.

  Each time the traveling load is sent from the traveling load acquisition unit 16, the torque command signal control unit 14 retrieves the traveling load from the “traveling load” column of Table 4. Whether the detected travel speed is slower than the target travel speed or acceleration that requires acceleration, or because the detected travel speed is equal to or higher than the target travel speed or when the vehicle is decelerating that requires constant speed or deceleration. In the case of acceleration, the control voltage in the same row as the searched traveling load in the column of “control voltage” during acceleration is read, and in the case of deceleration, the search in the column of “control voltage” during deceleration The control voltage in the same row as the travel load is read and determined. The control voltage determined in this way is directly input to the in-wheel motor 9 as a torque command signal.

  The torque command signal control means 14, the target travel speed acquisition means 11, the detected travel speed acquisition means 13, the acceleration acquisition means 15, and the travel load acquisition means 16 can be configured by a microcomputer. Tables 1 to 4 can also be implemented by a multidimensional array or the like stored on the memory of the microcomputer, and the required values can be obtained by accessing the multidimensional array or the like. Calculation processing is not necessary, and it is possible to use a low-cost microcomputer with low calculation capability.

  With the above configuration, the torque command signal control means 14 of the present embodiment directly determines the optimum control voltage (torque command signal) to be input to the electric motor according to the difference between the target travel speed and the detected travel speed. Can do. From the difference between the target travel speed and the detected travel speed, it can be estimated what kind of acceleration is necessary for the electric vehicle in order to quickly eliminate these differences. The acceleration a, the propulsive force P, the traveling load L, and the mass m of the electric vehicle are in a relationship of a = (P−L) / m, and the mass m is a constant during traveling. If the traveling load L received by the electric vehicle is known, the propulsive force P is also determined. Based on this, the optimum control voltage to be input to the in-wheel motor 9 can be determined. Therefore, instead of adjusting the control voltage that has been input to the in-wheel motor 9 until then, the control voltage is determined directly from the traveling load received by the electric vehicle due to hills and winds. It becomes possible to perform speed control with extremely high responsiveness to changes in speed and followability to changes in travel load.

  In the above embodiment, the case where the rotational speed of the rear wheel 2 detected by the rear wheel rotational speed detector 12 is converted to the detected traveling speed by the detected traveling speed acquisition means 13 has been shown. The speed of the electric vehicle with respect to the vehicle is such that a wheel for detecting a traveling speed that is unlikely to cause a slip or the like is provided separately from the rear wheel 2 or the traveling speed is detected by performing image processing on a road surface pattern that has been sequentially photographed. The detected travel speed may be obtained by another method.

  Further, in the above embodiment, the torque command signal control means 14 is classified into two types of acceleration time or deceleration time based on the difference between the target travel speed and the detected travel speed using Table 4, and the travel is performed for each case. Although the control voltage is determined from the load, for example, the deceleration time can be classified into constant speed driving and original deceleration, and the acceleration and deceleration can be further classified according to the degree of acceleration and deceleration, respectively. It can also be classified. Conversely, the traveling load is classified into a plurality of sizes according to the magnitude, and in each case, proportional control (P control) based on the difference between the target traveling speed and the detected traveling speed, PI control with integral control added thereto, etc. The conventional speed control may be performed. In this case, depending on the magnitude of the traveling load, for example, when the traveling load is large, a difference such as increasing the proportional control gain can be provided.

  In the above embodiment, the in-wheel motor 9 is a brushless DC motor. However, if the output torque is controlled by a torque command signal such as a control voltage, the type of the electric motor is Is optional. Furthermore, not only the in-wheel motor 9 directly connected to the axle of the rear wheel 2 as described above, but also other driving electric motors for driving the rear wheel 2 through a transmission device can be used.

  In the above embodiment, the torque command signal control means 14, the acceleration acquisition means 15, the traveling load acquisition means 16 and the like are configured by a microcomputer. However, these configurations are arbitrary, and a normal digital circuit, An analog circuit or other control means may be used.

  In the above embodiment, the electric vehicle in which the target traveling speed is instructed by the rotational speed of the pedal 6 has been described. However, for example, the target traveling speed is instructed by the rotational angle of the grip gripped by the hand of the handle 5. As long as the target travel speed is instructed by the above operation, it may be anything.

  In the above embodiment, the case where the electric vehicle is a four-wheel vehicle including the front wheel 1, the rear wheel 2, and the left and right auxiliary wheels 3, 3 is shown. However, the electric vehicle is a drive wheel driven by an electric motor. Can be any vehicle that has at least one wheel somewhere, such as a two-wheeled vehicle without auxiliary wheels 3, 3, a four-wheeled vehicle with two front and rear wheels, or a three-wheeled vehicle with two wheels at either front or rear. Good.

  The simulation result by the Example of the electric vehicle shown by the said embodiment is shown. This simulation is a case of starting on an uphill, and was performed under the same conditions as in the conventional example shown in FIG. However, the target travel speed was 4 km / h.

  In addition, since the acceleration cannot be calculated by the acceleration acquisition means 15 until the electric vehicle starts moving and the pulse is output twice from the rear wheel rotation speed detector 12, the control voltage until the acceleration is calculated depends on the traveling load. The value at the time of acceleration in the case of 0 is first output, and then 0.05V is added and output every 0.05 seconds.

  As shown in FIG. 3, the electric vehicle of the embodiment is at the time of acceleration shown in Table 4 when starting, so the control voltage of the in-wheel motor 9 is changed from the initial value of 3.45V (traveling load is 0N) to 4.10V. By gradually increasing the travel load to 35 N, the detected travel speed exceeds the target travel speed of 4 km / h after 1.7 seconds. Then, since the deceleration time shown in Table 4 is reached, the traveling load at that time becomes 25N, and the control voltage drops to 3.45V. In addition, the detected traveling speed starts to decrease, and the acceleration becomes slightly negative, so that the control voltage also decreases to 0.85V. However, if the detected travel speed becomes slightly slower than the target travel speed of 4 km / h after 2.0 seconds, the acceleration shown in Table 4 is resumed, and the control voltage is restored to 3.65 V. Thereafter, the detected travel speed is the target travel speed. The control voltage is adjusted so as to shift around 4 km / h of the traveling speed.

1 is a side view illustrating a configuration of an electric vehicle according to an embodiment of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram illustrating a configuration of speed control of an electric vehicle according to an embodiment of the present invention. FIG. 7 is a time chart illustrating an example of the present invention and illustrating a relationship between a control voltage and a traveling speed when starting uphill. It is a time chart which shows a prior art example, and shows the relationship between the control voltage at the time of flat ground start, and traveling speed. It is a time chart which shows a prior art example and shows the relationship between the control voltage at the time of starting uphill, and driving speed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Front wheel 2 Rear wheel 3 Auxiliary wheel 4 Saddle 5 Handle 6 Pedal 7 Loading platform 8 Storage battery 9 In-wheel motor 10 Pedal rotational speed detector 11 Target traveling speed acquisition means 12 Rear wheel rotational speed detector 13 Detected traveling speed acquisition means 14 Torque Command signal control means 15 Acceleration acquisition means 16 Travel load acquisition means

Claims (4)

In an electric vehicle driven by an electric motor in which a target travel speed (hereinafter referred to as “target travel speed”) is instructed by a driver's operation and output torque is controlled by a torque command signal,
Traveling speed detecting means for detecting the traveling speed of the electric vehicle;
An acceleration acquisition means for obtaining acceleration from a speed change per unit time of the traveling speed detected by the traveling speed detecting means (hereinafter referred to as “detected traveling speed”);
Travel load acquisition means for determining the travel load of the electric vehicle from the acceleration obtained by the acceleration acquisition means and the output torque of the electric motor;
A torque command signal to be input to the electric motor is generated so as to generate an output torque for obtaining an acceleration that eliminates the difference between the target travel speed and the detected travel speed in accordance with the travel load obtained by the travel load acquisition means. An electric vehicle comprising torque command signal control means for determining.   2. The electric vehicle according to claim 1, wherein the target travel speed is instructed according to a pedal rotation speed when the driver steps on the pedal with his / her foot to rotate the pedal. 3.   The electric vehicle according to claim 1, wherein the torque command signal is a control voltage.   The acceleration acquisition means, the running load acquisition means, and the torque command signal control means determine acceleration, running load, and torque command signal, respectively, based on a table created in advance. The electric vehicle according to any one of claims 1 to 3.

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