KR101308690B1 - Driving controlling system for a motor driven electric vehicle - Google Patents

Abstract

PURPOSE: An operation control system for a motor-driven electric vehicle prevents the injuries of passengers in advance by controlling driving and operating modes according to the loaded weight. CONSTITUTION: Multiple sensors are installed in a vehicle and sense the current condition of the vehicle. An encoder (109) measures the rotation number of a vehicle wheel. A pulse width modulation (PWM) control device (106) outputs a PWM control signal by setting the final PWM value. A PWM driver receives the PWM control signal and outputs a PWM signal. A motor (105) is driven by receiving the PWM signal. An acceleration pedal sensor senses the angle of an acceleration pedal (101). The PWM control device calculates and outputs the final and maximum PWM value with the ratio of the acceleration pedal angle. The PWM control signal is outputted at delay time intervals when it is determined as a start mode. The PWM control signal is outputted at delay time intervals when it is determined as a driving mode. When it is determined as a deceleration mode, the acceleration pedal angle is corrected. The maximum PWM value is limited according to the current condition of the vehicle. [Reference numerals] (103) Display; (105) Motor; (106) PWM control device; (110) Battery

Description

DRIVING CONTROLLING SYSTEM FOR A MOTOR DRIVEN ELECTRIC VEHICLE}

The present invention relates to a driving control system for a motor-driven electric vehicle, and more particularly, a driving mode suitable for sensing a state of a vehicle by mounting various sensors on a low-speed vehicle or a short-range vehicle driven by a motor. The present invention relates to a driving control system for a motor-driven electric vehicle which can remarkably improve driving stability by controlling a PWM signal of a motor according to a corresponding mode.

Short-range vehicles are being operated in places that are small and not intended for long distance travel. In particular, it is used in a variety of environments, such as golf courses, amusement parks, airports, stadiums, warehouses, short-distance freight transport, and special purpose fire and events.

Such short-range low-speed vehicles are typically electric vehicles that use a motor as driving power. Such an electric vehicle varies the current supplied to the motor by the inverter from a battery charged with a high voltage, and generates driving power by driving the motor according to the driving mode. At this time, the control unit for performing the overall control operation for generating the driving power of the motor receives the signal detected from the acceleration state and the brake state of the electric vehicle, and provides a PWM (Pulse Width Mudulation) signal corresponding to the drive of the motor To control.

That is, in the case of the electric vehicle or hybrid electric vehicle driven by the motor as described above, the motor driving control operation of the vehicle is an acceleration detecting unit or a brake detecting unit generating a motor driving signal or a motor driving blocking signal, and converting it into a current command to control the motor driving. It is composed of a control unit for supplying a signal. The flow is made to the motor which receives the driving control signal from the control unit and executes it, and the encoder which checks the current motor speed.

However, such a low-speed vehicle may cause battery drainage due to overload, sudden start, etc. due to misoperation of the vehicle operator, and cargo may drop or injury of the occupant may occur due to a shock generated during start and stop. . In particular, if you are a novice driver, a situation may occur that may cause problems in safe operation due to a shock (jerk).

Therefore, there is a need for a driving control system that is suitable for driving conditions of a low speed vehicle and ensures safe driving, and prevents a shock occurring during starting and stopping.

[Document 1] Republic of Korea Patent Publication No. 2003-0018877 Low speed control method for a motor-driven electric vehicle (Hyundai Motor Company) 2003.03.06

An object of the present invention is to provide a low speed vehicle driving control system that can increase the stability and economical efficiency of a low speed vehicle by controlling the driving and driving according to the load through a load cell provided between the vehicle body and the axle.

Another object of the present invention is to provide a low speed vehicle driving control system capable of minimizing shock and battery consumption in driving by controlling a PWM signal of a motor by angle sensing of a brake pedal and an accelerator pedal and measuring a vehicle speed through an encoder. .

Another object of the present invention is to provide a driving control system for a low speed vehicle that can prevent the erroneous operation of the driver due to a sudden pedal operation by applying a separate control algorithm according to the inclination by sensing the uphill and downhill inclination.

Still another object of the present invention is to provide a low speed vehicle driving control system capable of displaying danger and warning information that may occur in a vehicle by monitoring a temperature of a motor, a battery remaining amount, and the like.

In order to achieve the above-described object of the present invention and to achieve the specific effects of the present invention described below, the characteristic structure of the present invention is as follows.

According to an aspect of the present invention, a driving control system for a low speed vehicle, the encoder for measuring the rotational speed of the vehicle wheel; The vehicle speed is calculated from the number of revolutions of the vehicle wheel measured by the encoder, the starting state is determined from the change of the calculated speed, and when determined as the starting state, a PWM (Pulse Width Modulation) control signal according to a preset starting mode. PWM control device for outputting; A PWM driver for receiving a PWM control signal from the PWM control device and outputting a PWM signal for driving a motor; And a motor driven by receiving a PWM signal from the PWM driver.

Preferably, the PWM control device applies the start mode until the vehicle reaches a preset speed.

Preferably, the PWM control device, according to the start mode, outputs a differential PWM control signal at each preset delay time interval.

Preferably, the system further comprises a tilt sensor for sensing the inclination angle of the vehicle, the PWM control device, any one selected from the uphill mode, flat mode, downhill mode from the inclination angle of the vehicle sensed from the tilt sensor. Apply mode to output PWM control signal.

Preferably, the PWM control device outputs a PWM control signal divided more than the downhill mode in the uphill mode.

Preferably, the system further comprises an acceleration pedal sensor mounted on the pedal shaft of the accelerator pedal to sense the pedal angle of the accelerator pedal, wherein the PWM control device, the PWM control signal, the maximum PWM value and the acceleration Output by calculating the ratio of pedal angle

Preferably, the system further includes a brake pedal sensor mounted on the pedal shaft of the brake pedal to sense a pedal angle of the brake pedal, wherein the PWM control apparatus, the deceleration state is determined from the change in the calculated speed In addition, when it is determined that the deceleration state, the accelerator pedal angle for calculating the final PWM control signal according to the preset deceleration mode is corrected and applied by the following equation.

Where D1 'is the modified accelerator pedal angle, D1 is the actual accelerator pedal angle, and D2 is the brake pedal angle.

Preferably, the system further comprises a load cell for measuring the load between the axle and the vehicle body, wherein the PWM control device, if the load exceeds a preset value by the information received from the load cell, The maximum PWM value is limited to less than the first set value according to the set low speed mode application.

Preferably, the system further comprises a temperature sensor for measuring the temperature of the motor, the PWM control device, the predetermined low speed when the temperature exceeds a preset value by the information received from the temperature sensor Depending on the mode application, the maximum PWM value is limited to less than the first set value.

Preferably, the system further comprises a battery remaining amount measuring means for measuring the remaining amount of the battery, the PWM control device, if the remaining battery amount is less than a preset value by the information received from the battery remaining amount measuring means, The maximum PWM value is limited to less than the second set value according to the set power saving mode application.

As described above, the present invention has an advantage of reducing the battery consumption and preventing the risk of falling cargo or injury of the occupant by controlling the driving and driving mode according to the load loaded on the vehicle.

In addition, according to the present invention, by controlling the PWM signal of the motor by the angle sensing of the brake pedal and the accelerator pedal and the measurement of the vehicle speed through the encoder, it is possible to reduce the shock generated when starting and stopping and to induce safe driving. .

In addition, according to the present invention there is an advantage to ensure the safety by applying a control mode algorithm for preventing a driver's misoperation, such as sudden brake or sudden acceleration on the uphill and downhill slopes.

In addition, according to the present invention there is an advantage to inform the driver of danger and warning information that may occur in the vehicle by monitoring the temperature of the motor in the vehicle, the remaining amount of battery, and the like.

BRIEF DESCRIPTION OF THE DRAWINGS A brief description of each drawing is provided to more fully understand the drawings recited in the description of the invention.
1 and 2 are views showing the in-vehicle device configuration according to an embodiment of the present invention.
3 is a diagram illustrating an input / output terminal of a microprocessor implementing a PWM control apparatus according to an embodiment of the present invention.
4 is a diagram showing the detailed structure of a PWM control device according to an embodiment of the present invention.
5 and 6 are flowcharts illustrating a driving control procedure for a low speed vehicle according to an exemplary embodiment of the present invention.
7 is a diagram illustrating an example of a display screen of a display device according to an exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION The following detailed description of the invention refers to the accompanying drawings that show, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. It should be understood that the various embodiments of the present invention are different, but need not be mutually exclusive. For example, certain features, structures, and characteristics described herein may be implemented in other embodiments without departing from the spirit and scope of the invention in connection with an embodiment. It is also to be understood that the position or arrangement of the individual components within each disclosed embodiment may be varied without departing from the spirit and scope of the invention. Accordingly, the following detailed description is not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims, along with the full range of equivalents to which such claims are entitled. In the drawings, like reference numerals refer to the same or similar functions throughout the several views.

The present invention discloses a low speed vehicle driving control system and method for improving driving stability of a low speed vehicle or a short distance vehicle driven by a motor.

Particularly, in the present invention, various sensors are provided in a low-speed vehicle, and the data sensed from each sensor are combined to determine a current driving mode among a plurality of preset driving modes, and generate an optimal PWM control signal according to the driving mode. Thus, stable and economical driving control can be provided.

In this case, the sensors provided in the vehicle include a brake sensor provided on the brake pedal to sense the inclination angle of the brake pedal, an acceleration sensor provided on the accelerator pedal to sense the inclination angle of the accelerator pedal, and the inclination of the vehicle. It may be a tilt sensor that senses a state, an encoder that measures the number of revolutions of the vehicle wheel, a load cell that measures the load of the vehicle, and the like.

In addition, the driving mode set according to an embodiment of the present invention may be an uphill mode, a flat mode, a downhill mode, a low speed mode, a power saving mode, a start mode, a deceleration mode, a driving mode, and the like.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Hereinafter, a detailed description according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

1 and 2 are views showing the in-vehicle device configuration according to an embodiment of the present invention. 1 and 2, the low speed vehicle 100 to which the present invention is applied is driven by a motor 105, and receives a control signal from a PWM control device 106 in a driver to generate a PWM signal to the motor. to provide.

In this case, in the present invention, the PWM control device 106 collects information from various sensors installed in the vehicle to determine the current driving mode, and provides a stable and economical driving control by providing a control signal to the driver according to each driving mode. can do.

That is, according to the embodiment of the present invention, the PWM control device 106 receives the pedal angle information from the accelerator pedal 101 or the brake pedal 102. For example, a rotary volume sensor is mounted on a rotation shaft of each pedal, and the pedal signal converter converts information sensed from the pedal sensor into a rotation angle signal according to the rotation angle of the pedal to provide the PWM control device 106.

In addition, the PWM control device 106 is provided with the tilt angle information of the vehicle from the tilt sensor 107. The information provided from the tilt sensor 107 may determine whether the road surface on which the vehicle is currently running is uphill, flat, or downhill.

In addition, the PWM control device 106 may be provided with a value obtained by converting the number of revolutions of the wheel (1000 pulses / 1 revolution) into RPM (rpm) from an encoder 109 provided on the vehicle wheel shaft. . The information provided from the encoder 109 may measure the speed of the current vehicle.

In addition, the PWM control device 106 may receive load information of the vehicle from a load cell 108 provided between the axle and the vehicle body.

On the other hand, the information collected by the PWM control device 106 may be provided to the display device 103, the display device 103, as shown in Figure 7, the driving mode information or speed, load, temperature of the current vehicle Information may be provided to the driver by displaying the battery status information.

As such, the PWM control device 106 collects various driving-related information (eg, acceleration information, deceleration information, vehicle speed, load, slope, etc.) from various sensors provided in the vehicle, and based on the collected information, After determining the driving mode, a PWM control signal is generated and provided to the driver according to a preset control method for each driving mode.

By doing so, it is possible to enable the optimum running control suitable for the current running state of the low speed vehicle.

3 is a diagram illustrating an input / output terminal of a microprocessor implementing a PWM control apparatus according to an embodiment of the present invention. Referring to FIG. 3, the PWM control apparatus according to the embodiment of the present invention may be implemented as an embedded microprocessor.

That is, due to the development of electronic technology, various types of sensors may be provided according to an embodiment of the present invention, and a memory, an I / O control, a control, a digital / analog conversion circuit, a communication circuit, etc. may be provided around a microprocessor. This can be divided into a PCB.

In addition, by integrating these peripheral circuits with the embedded microprocessor illustrated in FIG. 3 as in another embodiment, a microprocessor may be connected to control the peripheral sensor and the driving device. Accordingly, it is possible to reduce the occurrence of failure, to reduce the PCB size, and to be more high performance.

As shown in FIG. 3, signals from the I / O pins of the embedded microprocessor and the temperature, load, encoder, and angle sensor signal processing devices are connected to each port. In addition, by providing a signal output from the microprocessor to the LCD display panel, it is possible to provide information and warning display of the vehicle status as shown in FIG.

In addition, according to an embodiment of the present invention, the PWM motor signal is controlled by providing a PWM control signal to the driver through a clock inside the microprocessor and a digital to analog (DA) device.

Meanwhile, according to an exemplary embodiment of the present invention, the microprocessor determines a driving mode by combining various types of sensor information input by the method described below with reference to FIGS. 5 and 6, and outputs an optimal PWM control signal according to each driving mode. do.

In this case, the sensor input signal processing in the microprocessor may be processed as follows, for example.

Tilt sensor: DO port of the microprocessor

2. Temperature sensor: microprocessor DC 5V full scale converting after low current differential amplifier processing

3. Load sensor: treated in the same way as number 2

4. Battery level sensor: handle in the same way

5. PWM output: converts motor driver drive voltage to DA port of microprocessor

6. Delay: Microprocessor internal timer processing

7. Acceleration / Brake Signal: Microprocessor DI Port

8. Encoder (speed): Counter processing of DI port of microprocessor and internal setting internal timer

4 is a diagram showing the detailed structure of a PWM control device according to an embodiment of the present invention. Referring to FIG. 4, the PWM control device 106 according to an embodiment of the present invention includes a sensor information receiver 410, an inclination determiner 420, a speed calculator 430, a mode determiner 440, and a control signal. It may be configured to include a generation unit 450 and the like.

The sensor information receiver 410 performs a function of receiving information sensed from various sensors provided in a vehicle according to an exemplary embodiment of the present invention. In this case, a signal sensed directly from each sensor may be provided or may be provided after signal processing of the sensed signal.

The inclination determination unit 420 determines whether the current downhill T3, the uphill T1, or the flat T2 is provided to the mode determination unit 440 according to the inclination angle information provided from the tilt sensor. The speed calculator 430 calculates the speed of the current vehicle from the information provided from the encoder, and determines whether the current vehicle is in the starting state, the acceleration state, or the deceleration state by calculating the acceleration from the change value of the speed.

The mode determiner 440 is provided with various types of information (eg, load information, temperature information, remaining battery information, angle information D1 of the accelerator pedal, and brake angle information D2) received from the sensor information receiver 410. The current vehicle inclination angle and the speed or acceleration information is received from the inclination determination unit 420 and the speed calculator 430, and the current vehicle inclination is determined. Mode, flat mode, downhill mode, low speed mode, power saving mode, start mode, deceleration mode, driving mode and the like.

The control signal generator 450 generates an optimal PWM control signal according to the mode information determined by the mode determiner 440 and outputs the optimal PWM control signal to the driver.

On the other hand, the respective components of the PWM control device 106 are separately shown in the drawings to show that they can be functionally and logically separated, meaning that they are physically necessarily separate components or implemented in a separate code It is not.

In this specification, each functional unit (or module) may mean a functional and structural combination of hardware for performing the technical idea of the present invention and software for driving the hardware. For example, each functional unit may mean a logical unit of a predetermined code and a hardware resource for performing the predetermined code, and does not necessarily mean a physically connected code or a kind of hardware. It can be easily inferred by the average expert in the art.

Hereinafter, a low speed vehicle driving control procedure according to an embodiment of the present invention will be described with reference to FIGS. 5 and 6.

First, referring to FIG. 5, the vehicle sensor state is detected by collecting information from various sensors installed in the vehicle (S501). First, the value received from the tilt sensor is determined (S502), and if the inclination exceeds 0 (S503), and if the inclination is 0, it is set to the flat mode (T2) (S504), If the inclination is less than 0, it is set to the downhill mode (T3) (S505).

Then, the accelerator pedal angle D1 and the brake pedal angle D2 are measured (S506, S507) from the sensors provided in the accelerator pedal and the brake pedal, respectively.

On the other hand, the load is in a good state below the preset value by the information received from the load cell (S508), or the temperature is in a good state below the preset value by the information received from the temperature sensor (S509), or the battery remaining amount measuring means When the battery remaining amount is in a good state in which the remaining battery level exceeds a preset value (S511), the maximum PWM value (Max. PWM) is set to less than 100%.

On the other hand, when the load exceeds a preset value by the information received from the load cell, or when the temperature exceeds the preset value by the information received from the temperature sensor, the low speed mode (S510) is applied because it is not in a good state. . That is, set the maximum PWM value to less than 50%.

Further, when the remaining battery level is less than or equal to the preset value based on the information received from the battery remaining amount measuring means, the maximum PWM value Max.PWM is set to less than 30% as the power saving mode S512.

As such, when the uphill mode, the flat mode, the downhill mode, the low speed mode, the power saving mode, etc. are set according to the procedure of FIG. 5, the mode according to the vehicle speed is set next according to the procedure of FIG. 6.

Referring to FIG. 6, after the driving mode is primarily determined according to FIG. 5, the acceleration and deceleration states of the vehicle are determined based on the information received from the encoder (S601) to add a start mode, a driving mode, a deceleration mode, and the like. Decide on

That is, when the speed of the vehicle continues to increase from zero, it may be determined as a start mode (S602). In the start mode, the vehicle can be stably started by performing initial PWM control up to the target RPM in order to reduce the jerk according to an embodiment of the present invention (S603).

The initial PWM control method may proceed as follows, for example.

1) PWM 3%-> Delay 10->

2) PWM 2%-> Delay 10->

3) PWM 5%-> Delay 10->

4) PWM 10%-> Delay 5->

5) PWM 5%

In this manner, when the vehicle starts, the PWM control is controlled according to the start mode, so that even in the case of an inexperienced person, the vehicle can be safely started without jerk.

In addition, when the speed of the vehicle maintains a constant speed, it may be determined as a driving mode (S604). In the driving mode, PWM control may be performed at a delay interval of 10 according to an embodiment of the present invention.

In addition, when the speed of the vehicle continues to decrease from zero to a certain speed, it may be determined as the deceleration mode (S605). In the deceleration mode, the angle D1 of the accelerator pedal may be replaced with a value of Equation 1 below to prevent a false operation of the accelerator pedal according to the exemplary embodiment of the present invention.

In Equation 1, D1 'is the angle of the modified accelerator pedal, D1 is the angle of the actual accelerator pedal, and D2 is the angle of the brake pedal.

That is, referring to Equation 1, when it is determined that the deceleration mode, when the driver stepped on the accelerator pedal, the driver does not reflect the angle of the accelerator pedal actually stepped on, but instead the acceleration that the driver actually stepped on. The pedal angle can be reduced by 50%, and the brake pedal angle can be further reflected by the accelerator pedal angle. Therefore, even if the accelerator pedal is misoperated while the low speed vehicle is decelerating, vehicle driving safety can be achieved.

In the deceleration mode, PWM control may be performed at an interval of 5 delays according to an embodiment of the present invention.

On the other hand, when the current driving mode is determined from the values provided from the various sensors as described above, the PWM control signal may be calculated by the angle ratio of the accelerator pedal and output to the motor driver.

For example, the PWM control signal may be generated by calculating S606 as PWM = Max. PWM: D1. Of course, in the deceleration mode, the modified acceleration pedal angle D1 'is applied to D1.

As such, when the PWM control signal is generated, it is possible to control by dividing the PWM by 60 in the uphill (T1) and 40 in the downhill (T3). Accordingly, the vehicle is operated by calculating and applying an appropriate PWM value for each driving mode (S607).

In this way, the vehicle driving situation can be determined in real time through various sensors and controllers (axels / brakes), and intelligent PWM can control the irregular and unsafe acceleration pedals / brake pedals for driving safety. This prevents jerks and ensures a stable start and enables PWM control to reduce battery consumption.

7 is a diagram illustrating an example of a display screen of a display device according to an exemplary embodiment of the present invention. Referring to FIG. 7, three pieces of information for each sensor may be displayed as state contents (for example, good, caution, and danger) using LEDs, and in a dangerous state, a program algorithm may be implemented to perform logic corresponding to each mode.

The various operations and functions as described herein with respect to the various methods may be performed by any of a number of types of functions, such as a particular processing function and / or a processing function implemented therein, and / ≪ / RTI > For example, such functions may be performed by various operations and processes as described herein, or by performing any other operations and functions as described herein, or the like, as well as performing each of the equivalents thereof, And may perform such operations, processes, and the like.

The present invention has been described above with the aim of method steps indicative of the performance of certain functions and their relationships. The boundaries and order of these functional components and method steps have been arbitrarily defined herein for convenience of description. Alternative boundaries and sequences may be defined as long as the specific functions and relationships are properly performed. Any such alternative boundaries and sequences are therefore within the scope and spirit of the claimed invention.

As described above, the present invention has been described by specific embodiments such as specific components and the like. For those skilled in the art, various modifications and variations are possible from these descriptions.

Accordingly, the spirit of the present invention should not be construed as being limited to the embodiments described, and all of the equivalents or equivalents of the claims, as well as the following claims, belong to the scope of the present invention .

100: low speed vehicle 101: acceleration pedal
102: brake pedal 103: display device
104: reducer 105: motor
106: PWM control device 107: Tilt sensor
108: load cell 109: encoder
110: battery 410: sensor information receiver
420: slope determination unit 430: speed calculation unit
440: mode determination unit 450: control signal generation unit

Claims (10)

In a driving control system for a motor-driven electric vehicle,
A plurality of sensors installed in the vehicle to sense a current state of the vehicle;
An encoder for measuring the rotation speed of the vehicle wheel;
Collecting information sensed from the plurality of sensors to determine the current state of the vehicle and to calculate the vehicle speed from the number of revolutions of the vehicle wheel measured by the encoder, the starting mode, the driving mode of the vehicle from the change in the calculated speed And a PWM control device that determines whether the deceleration mode is applicable, and outputs a PWM (Pulse Width Modulation) control signal by setting a final PWM value according to the determined mode.
A PWM driver for receiving a PWM control signal from the PWM control device and outputting a PWM signal for driving a motor; And
And a motor driven by receiving a PWM signal from the PWM driver.
The plurality of sensors includes an accelerator pedal sensor mounted on the pedal shaft of the accelerator pedal to sense the pedal angle of the accelerator pedal,
The PWM control device,
Calculates and outputs the final PWM value as the ratio between the maximum PWM value and the accelerator pedal angle,
When it is determined that the departure mode, the predetermined differential PWM control signal is output for each preset delay time interval,
When the driving mode is determined, a PWM control signal is output at every predetermined delay time.
When the deceleration mode is determined, the accelerator pedal angle for calculating the final PWM value is corrected and applied.
And the maximum PWM value is limited and applied according to the current state of the vehicle determined based on the information sensed by the plurality of sensors.
The method according to claim 1, wherein the PWM control device,
And apply the starting mode until the vehicle reaches a preset speed.
delete The method of claim 1, wherein the plurality of sensors comprises a tilt sensor for sensing the inclination angle of the vehicle,
The PWM control device,
And a PWM control signal is output by applying any one selected from the inclination angle of the vehicle sensed by the tilt sensor to the uphill mode, the flat mode, and the downhill mode.
delete delete The method of claim 1, wherein the plurality of sensors include a brake pedal sensor mounted on the pedal shaft of the brake pedal to sense the pedal angle of the brake pedal;
The PWM control device,
And the accelerator pedal angle in the deceleration mode is corrected by the following equation.

Where D1 'is the modified accelerator pedal angle, D1 is the actual accelerator pedal angle, and D2 is the brake pedal angle.
The method of claim 1, wherein the plurality of sensors includes a load cell for measuring the load between the axle and the vehicle body,
The PWM control device,
And when the load exceeds a preset value by the information received from the load cell, limiting the maximum PWM value to less than the first set value according to application of a preset low speed mode.
The method of claim 1, wherein the plurality of sensors comprises a temperature sensor for measuring the temperature of the motor,
The PWM control device,
And when the temperature exceeds a preset value by the information received from the temperature sensor, limiting the maximum PWM value to less than the first set value according to application of a preset low speed mode.
The method of claim 1, wherein the plurality of sensors includes a battery remaining amount measuring means for measuring the remaining amount of the battery,
The PWM control device,
And when the remaining battery level is less than a preset value by the information received from the remaining battery level measuring means, limiting the maximum PWM value to less than the second set value in accordance with application of a preset power saving mode.

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