Control device for electric vehicle

Abstract

This control device for an electric vehicle comprises: a region-specific estimated road surface friction coefficient setting unit that estimates and sets a road surface friction coefficient for each region on the basis of travel environment information; a slip suppression control unit; and a reaction force instruction unit. The slip suppression control unit comprises: a slip vibration detection unit that detects slip vibration from motor vibration; and a motor estimated road surface friction coefficient setting unit that estimates and sets a road surface friction coefficient on the basis of the detected slip vibration. The reaction force instruction unit comprises: a variation calculation unit that calculates a variation of the road surface friction coefficient for each region; a reaction force instruction value setting unit that compares the variation of the road surface friction coefficient for each region and a first threshold value and, if the variation exceeds the first threshold value, sets a reaction force instruction value for generating a strong reaction force compared to when the variation is less than the first threshold value; and a reaction force instruction unit that outputs a command signal of the reaction force instruction value to a reaction force application unit if the road surface friction coefficient is less than or equal to a second threshold value.

Description

Electric vehicle control device

[0001] The present invention relates to a control device for an electric vehicle that has a function of determining whether or not slip has occurred.

[0002] When a vehicle is traveling, slip occurs when the driving force applied to the tires of the drive wheels (referred to as "drive tires") exceeds the grip force from the road surface acting on the drive tires (referred to as "road grip force"). As shown in Figure 7, the driving force P of the drive tires (front wheels in the figure) of vehicle M is calculated as follows: P = T / r (1) where T is torque and r is the effective radius of the drive tires.

[0003] The road grip force F is calculated as follows: F=μ·Wf (2) where μ is the road friction coefficient, Wf is the vehicle weight applied to the driving tires (front wheels), and in FIG. 7, W is the total vehicle weight, and Wr is the vehicle weight applied to the driven tires (rear wheels).

[0004] Therefore, as shown in Figure 8, on dry paved roads, it is relatively easy to control driving so that the driving force P does not exceed the road grip force F (P≦F). If the relationship P≦F is always maintained, it is possible to continue driving without causing slippage.

[0005] On the other hand, on unpaved roads, the tire's road grip force F decreases, so the relationship P > F is likely to occur. Therefore, it is often difficult to drive on unpaved roads without slipping.

[0006] Even if the vehicle M is an electrically powered vehicle such as an electric vehicle (EV), a fuel cell vehicle (FCV), or a hybrid electric vehicle (HEV), slippage can be prevented by always maintaining the relationship P≦F when the vehicle is driven.

[0007] The drive force of electric vehicle drive motors is often controlled using vector control. Vector control separates the current flowing through the motor into a current component that generates torque (torque current component) and a current component that generates magnetic flux in the rotor (magnetic flux current component), and controls each component independently. Therefore, the drive force P of the drive tires can be quickly estimated from the torque current component flowing through the motor.

[0008] On the other hand, when the drive tires spin (slip), the motor torque fluctuates, causing high-frequency vibrations (slip vibrations) in the motor rotation speed. The road surface μ can be estimated from this slip vibration. Furthermore, when slip vibrations are detected, it can be estimated that the grip force of the drive tires is relatively reduced. As is clear from the above equation (2), when the vehicle weight Wf is constant, the road grip force F of the tires is determined by the road surface μ.

[0009] For example, Japanese Patent Application Laid-Open Publication No. 2013-112192 discloses a technology in which, when vehicle slippage is detected from the difference between the rotational speed of the drive wheels and the rotational speed of the driven wheels, a reaction force control device applies a reaction force to the accelerator pedal to notify the driver that a slippage has occurred.

[0010] However, as shown in Figure 8, the surface conditions of unpaved roads are not uniform, and there are various conditions in parts, such as gravel roads, sandy areas, and muddy areas. The friction coefficient also varies depending on the road surface conditions. Furthermore, there are also cross-roads where the friction coefficients of the road surfaces where the left and right drive wheels come into contact differ.

[0011] In the technology disclosed in Japanese Patent Application Laid-Open No. 2013-112192, when a reaction force control device detects a slip, the reaction force applied to the accelerator pedal is set regardless of changes in the actual road friction coefficient, making it difficult to accurately notify the driver that a slip has occurred.

[0012] In view of the above circumstances, an object of the present invention is to provide a control device for an electric vehicle that can accurately notify the driver of the occurrence of slippage.

[0013] One aspect of the present invention is a vehicle including a driving environment detection unit that detects the driving environment ahead of an electric vehicle, a vibration detection unit that detects motor vibrations generated in the rotation speed of a drive motor mounted on the electric vehicle, a reaction force application unit that applies a reaction force to an operation unit operated by a driver, an area-specific estimated road surface friction coefficient setting unit that estimates and sets an area-specific road surface friction coefficient based on the driving environment information detected by the driving environment detection unit, a slip suppression control unit, and a reaction force instruction unit, wherein the slip suppression control unit includes a slip vibration detection unit that detects slip vibrations from the motor vibrations detected by the vibration detection unit, and a reaction force instruction unit that, when the slip vibration is detected by the slip vibration detection unit, estimates the road surface friction coefficient based on the slip vibration. the reaction force instruction unit comprises a variation calculation unit that calculates the variation in the road surface friction coefficient by region detected by the region-by-region estimated road surface friction coefficient setting unit; a reaction force instruction value setting unit that compares the variation in the road surface friction coefficient by region calculated by the variation calculation unit with a first threshold value, and if the variation exceeds the first threshold value, sets a reaction force instruction value that generates a stronger reaction force than when the variation is below the first threshold value; and a reaction force command unit that outputs a command signal for the reaction force instruction value set by the reaction force command value setting unit to the reaction force application unit if the road surface friction coefficient set by the motor-estimated road surface friction coefficient setting unit is equal to or less than a second threshold value.

[0014] Schematic diagram of a drive control device mounted on an electric vehicle Flowchart showing the routine for setting the initial estimated road surface μ value Flowchart showing the routine for setting the estimated road surface μ with a camera by region Flowchart showing the routine for slip suppression control Conceptual diagram of a basic road surface μ setting map based on road type Conceptual diagram of a weather correction coefficient setting map Conceptual diagram of a tire correction coefficient setting map Conceptual diagram of an estimated road surface μ setting map based on road surface conditions Explanatory diagram showing the relationship between the driving force of the drive tires and road grip force Explanatory diagram showing the relationship between the driving force applied to the drive tires and road grip force when traveling on paved and unpaved roads

[0015] An embodiment of the present invention will be described below with reference to the drawings. Note that the drawings are schematic, and the relationship between the thickness and width of each member, the thickness ratio of each member, etc., differ from the actual ones. Of course, the drawings also include portions in which the dimensional relationships and ratios differ from one another.

[0016] 1, reference numeral 1 denotes a drive control device. This drive control device 1 is mounted on a host vehicle M (see FIG. 7). The host vehicle M is an electric vehicle. In the following description, the host vehicle M will be referred to as the electric vehicle M.

[0017] The drive control device 1 has a vehicle integrated control unit 2. This vehicle integrated control unit 2 comprehensively performs various controls related to the drive of the electric vehicle M. A camera control unit 3 is connected to the input side of this vehicle integrated control unit 2. Although not shown, various sensors that acquire information required when driving the electric vehicle M are also connected to the vehicle integrated control unit 2.

[0018] Furthermore, a torque sensor 4 serving as a steering operation detector and a vibration sensor 14a serving as a vibration detector are connected to the input side of the vehicle integrated control unit 2. The torque sensor 4 detects the torque generated when the driver operates a steering wheel 31c provided in an operation unit 31. The vibration sensor 14a detects the vibration (hereinafter referred to as "motor vibration") [Hz] generated in the rotation speed of a drive motor 14 (described later).

[0019] An inverter control unit 5 and a pressure actuator 8 serving as a reaction force applying unit are connected to the output side of the vehicle integrated control unit 2. Although not shown, the vehicle integrated control unit 2 is connected to various control units so as to be able to communicate bidirectionally.

[0020] Each control unit 2, 3, 5 is composed of a microcontroller equipped with a CPU, RAM, ROM, rewritable non-volatile memory (flash memory or EEPROM), and peripheral devices. The ROM stores programs and fixed data necessary for the CPU to execute various processes. The RAM serves as a work area for the CPU, temporarily storing various data for the CPU. The CPU is also called an MPU (microprocessor) or processor. A GPU (graphics processing unit) or a GSP (graph streaming processor) may be used instead of the CPU. Alternatively, a CPU, GPU, and GSP may be selectively combined.

[0021] An inverter 12 of an electric powertrain 11 is connected to the inverter control unit 5. The electric powertrain 11 includes the inverter 12, a high-voltage battery 13, and a drive motor 14. The inverter 12 is operated by a command signal from the inverter control unit 5. In accordance with the command signal from the inverter control unit 5, the inverter 12 converts direct current (DC) power from the high-voltage battery 13 into alternating current (AC) power and supplies it to the drive motor 14. The inverter control unit 5 controls the driving force of the drive motor 14 by vector control.

[0022] The output shaft 21 of the drive motor 14 is connected to drive shafts 22l, 22r of left and right drive wheels Fl, Fr via a differential Df. The drive motor 14 drives the drive wheels Fl, Fr with power supplied from the inverter 12, thereby powering the electric vehicle M.

[0023] Reference numeral 31 denotes an operating unit. This operating unit 31 is operated by the driver and comprises an accelerator pedal 31a and a brake pedal 31b for setting the vehicle speed, and a steering wheel 31c for setting the direction of travel. Of these, a pressure actuator 8 is connected to the accelerator pedal 31a and the brake pedal 31b. This pressure actuator 8 applies a reaction force to the accelerator pedal 31a and the brake pedal 31b in accordance with a command from the vehicle integrated control unit 2.

[0024] A camera unit 6 serving as a driving environment detection unit is installed at the front of the electric vehicle M. The camera unit 6 includes a stereo camera consisting of a main camera 6a and a sub-camera 6b.

[0025] The camera control unit 3 acquires information about the driving environment ahead of the electric vehicle M by image processing of images of the driving environment ahead of the electric vehicle M taken by both cameras 6a, 6b. Furthermore, information about the currently mounted tires is stored in the nonvolatile memory 3a provided in the camera control unit 3. This tire information is input by the user or driver when the tires are mounted. The tire information includes the type of tire, when it should be replaced, etc. The type of tire includes whether it is a normal tire or a studless tire, the tire size, etc.

[0026] Furthermore, various maps are stored in the nonvolatile memory 3a. These maps include a basic road surface μ setting map (see FIG. 5A), a weather correction coefficient setting map (see FIG. 5B), and a tire correction coefficient setting map (see FIG. 5C), which are read when setting the initial estimated μ value. Furthermore, the nonvolatile memory 3a also stores an estimated road surface μ setting map (see FIG. 6).

[0027] As shown in Figure 5A, the basic road surface μ map stores basic road surface μ data set in advance for each road type. Road types include paved roads (concrete roads, asphalt roads), unpaved roads (gravel roads, dirt roads), etc. The basic road surface μ for unpaved roads is set lower than that for paved roads.

[0028] As shown in Fig. 5B, the weather correction coefficient setting map has correction coefficients set according to the weather (however, the correction coefficient is ≦ 1). The correction coefficients are set to decreasing values ​​in the order of sunny weather > cloudy weather > rainfall > snowfall.

[0029] As shown in Fig. 5C, the tire correction coefficient setting map has correction coefficients (however, the correction coefficient is 1 or less) set according to the tire type. The correction coefficient is set higher for normal tires than for studless tires. Also, the higher the aspect ratio of the tire, the higher the correction coefficient is set.

[0030] As shown in Figure 6, the estimated road surface μ setting map sets estimated road surface μ according to road surface conditions. This road surface condition is based on an image of the road ahead captured by the camera unit 6, and one frame of image data is divided into regions for each road surface condition by image recognition using, for example, AI (artificial intelligence). This road surface condition is information obtained in real time for each region regarding the current road surface conditions, such as paved roads, unpaved roads (including roads under construction), metal joints at bridge joints, snow, fallen leaves, etc.

[0031] A navigation system 7 is also connected to the camera control unit 3. This navigation system 7 has road map data. The navigation system 7 acquires vehicle position information (latitude, longitude, and altitude) based on GNSS (Global Navigation Satellite System) satellites. The navigation system 7 then plots the acquired vehicle position on the road map data and estimates the current vehicle position and traveling direction on the road map. Therefore, the navigation system 7 functions as a vehicle position detection unit of the present invention.

[0032] The navigation system 7 also acquires information about the surrounding environment around the vehicle based on road map data. This information about the surrounding environment includes static information and dynamic information. Static information includes road surface information such as paved roads and unpaved roads. Dynamic information includes real-time weather information. Weather information includes weather conditions such as sunny, rainy, and snowy weather, sunshine conditions, rainfall, snowfall, temperature, humidity, and air pressure. Weather information may also be acquired from weather information provided on a website. Therefore, the navigation system 7 also functions as the environmental information acquisition unit of the present invention.

[0033] The camera control unit 3 sets an estimated μ initial value for the road along which the electric vehicle M will travel, by referring to a map stored in the non-volatile memory 3a, based on static information and dynamic information about the vicinity of the vehicle's position input from the navigation system 7. The camera control unit 3 then corrects the area-specific basic road surface μ recognized based on the image captured by the camera unit 6 with the estimated μ initial value to set an area-specific camera-estimated road surface μc. The camera control unit 3 outputs data of the set area-specific camera-estimated road surface μc to the vehicle integrated control unit 2.

[0034] The vehicle integrated control unit 2 detects slip vibration from motor vibrations occurring in the rotational speed of the drive motor 14. When slip occurs on the drive wheels Fl and Fr, the motor torque fluctuates suddenly. This fluctuation in motor torque causes torsional resonance (rotational speed vibration) in the motor rotating shaft. In particular, when slip occurs, high-frequency vibrations (slip vibrations) are detected.

[0035] The vehicle integrated control unit 2 sets an estimated road surface μ based on this slip vibration. If this estimated road surface μ is equal to or less than a predetermined threshold, a reaction force is applied to the accelerator pedal 31 a and the brake pedal 31 b. This reaction force alerts the driver to the occurrence of slip, and by limiting the depression of the accelerator pedal 31 a and the brake pedal 31 b, the occurrence of slip is suppressed.

[0036] Specifically, the camera control unit 3 sets the estimated μ initial value in accordance with the estimated road surface μ initial setting routine shown in FIG. 2. The camera control unit 3 reads the vehicle position information detected by the navigation system 7 (21). Next, the camera control unit 3 acquires the road type around the vehicle position from the road map data (step S2). The road map data stores road types such as paved roads and unpaved roads. Paved roads are further classified into concrete roads, asphalt roads, etc. Unpaved roads are further classified into gravel roads, dirt roads, etc.

[0037] Thereafter, the camera control unit 3 refers to the basic road surface μ map (FIG. 5A) based on the road type and sets the basic road surface μ corresponding to the acquired road type (step S3). The basic road surface μ map stores road surface μ values ​​set for each road type that have been obtained in advance through experiments or the like.

[0038] The current weather information for the vehicle's location is also acquired from dynamic information in road map data or weather information provided on a website (step S4).Then, based on this weather information, the weather correction coefficient is set by referring to the weather correction coefficient setting map (FIG. 5B) (step S5).

[0039] Furthermore, the camera control unit 3 sets the tire correction coefficient by referring to the tire correction coefficient setting map (FIG. 5C) based on the tire information of the electric vehicle M stored in advance in the nonvolatile memory 3a (step S6).

[0040] Thereafter, the camera control unit 3 multiplies the basic road surface μ by the average value of the weather correction coefficient and the tire correction coefficient, or the lower value, to set an initial value of the estimated road surface μ (step S7), and then exits the routine. Note that the processing in step S7 corresponds to the estimated road surface friction coefficient initial value setting unit of the present invention. Also, the camera control unit 3 sets the area-specific camera-estimated road surface μc based on the image captured by the camera unit 6. Specifically, this area-specific camera-estimated road surface μc is set according to the area-specific camera-estimated road surface μc setting routine shown in FIG. Note that the processing in this routine corresponds to the area-specific estimated road surface friction coefficient setting unit of the present invention.

[0041] In this routine, the camera control unit 3 reads in a camera image captured by the camera unit 6 and subjected to predetermined image processing (step S11). Then, for each frame of this camera image, the road is divided into image regions based on each feature, using, for example, AI (artificial intelligence), and the road surface conditions of each divided image region are identified (step S12). As shown in FIG. 8 , the road surface conditions of an unpaved road are not uniform, and there are various partial conditions, such as gravel, sand, mud, snow, and fallen leaves. In particular, the conditions of road surfaces such as mud, snow, and fallen leaves change in real time. Furthermore, the conditions may differ on road surfaces where the left and right drive wheels F1 and Fr meet, such as on a straddle road. The camera control unit 3 divides one frame image into road conditions.

[0042] Next, the camera control unit 3 sets the estimated road surface μ for each area based on the road conditions for each area by referring to the estimated road surface μ setting map shown in Figure 6 (step S13). Next, the camera control unit 3 reads the initial estimated road surface μ value set in the initial estimated road surface μ value setting routine (step S14).

[0043] Then, the camera control unit 3 corrects the estimated road surface μ set for each region with the initial estimated road surface μ value to set the camera estimated road surface μc for each region (step S15), and exits the routine.

[0044] This area-specific camera-estimated road surface μc is read by the vehicle integrated control unit 2. When the vehicle integrated control unit detects the occurrence of a slip, it executes slip suppression control to apply a reaction force to the accelerator pedal 31a and the brake pedal 31b.

[0045] Specifically, this slip prevention control is executed in accordance with a slip prevention control routine shown in Fig. 4. The processing in this routine corresponds to the slip prevention control unit of the present invention.

[0046] The vehicle integrated control unit 2 first reads the motor vibration [Hz] detected by the vibration sensor 14a (step S21). This vibration sensor 14a detects the vibration [Hz] occurring in the rotation speed of the drive motor 14. The vehicle integrated control unit 2 then checks whether or not slip vibration is occurring in the drive motor 14 based on the motor vibration [Hz] detected by the vibration sensor 14a (step S22). If a sudden torque fluctuation occurs in the drive motor 14, vibration occurs in the rotation speed of the drive motor 14. If the drive wheels Fl and Fr spin (slip), high-frequency motor vibration occurs in the rotation speed of the drive motor 14.

[0047] Then, if the motor vibration is equal to or greater than the set frequency, the vehicle integrated control unit 2 determines that slip vibration is present (step S22: YES). On the other hand, if the motor vibration is less than the set frequency, the vehicle integrated control unit 2 determines that slip vibration is absent (step S22: NO). If it is determined that slip vibration is absent (step S22: NO), the routine is exited. The processing in step S22 corresponds to the slip vibration detection unit of the present invention.

[0048] If the vehicle integrated control unit 2 determines that slip vibration is present (step S22: YES), it sets an estimated road surface μm (hereinafter referred to as "motor estimated road surface μm"), which is an estimated value of road surface friction coefficient (step S23). Slippage (slip) of the drive wheels F1 and Fr occurs when the relationship P (driving force) > F (road surface grip force) is established. The driving force P of the drive wheels F1 and Fr can be calculated quickly from the torque current component of the drive motor 14. The vehicle integrated control unit 2 sets the motor estimated road surface μm based on the driving force P when slippage of the drive wheels F1 and Fr is detected and the frequency [Hz] when slip vibration is detected. The processing in step S23 corresponds to the motor estimated road surface friction coefficient setting unit of the present invention.

[0049] Thereafter, the vehicle integrated control unit 2 checks whether the driver is operating the steering wheel 31c (step S24). Whether the driver is operating the steering wheel 31c is determined based on, for example, the output value of the torque sensor 4, and if the output value is equal to or greater than a predetermined value, it is determined that the steering wheel 31c is being operated.

[0050] If the vehicle integrated control unit 2 determines that the driver is operating the steering wheel 31c (step S24: YES), it sets the reaction force generation threshold μst, which serves as a second threshold, to a high value μh (μst←μl: step S25). By setting the reaction force generation threshold μst to a high value μh when the driver is operating the steering wheel 31c, reaction forces can be applied to the accelerator pedal 31a and the brake pedal 31b at an early timing. This makes it possible to suppress slippage even if the driver's operation of the steering wheel 31c tends to exacerbate the occurrence of slippage.

[0051] Furthermore, if the vehicle integrated control unit 2 determines that the driver is not operating the steering wheel 31c (step S24: NO), it sets the reaction force generation threshold μst to the normal value μn (μst←μn: step S26). The processing in steps S24 to S26 corresponds to the second threshold setting unit of the present invention.

[0052] The vehicle integrated control unit 2 then compares the motor-estimated road surface μ with the reaction force generation threshold μ (step S27). If it determines that the motor-estimated road surface μ exceeds the reaction force generation threshold μ (NO), it exits the routine. If it determines that the motor-estimated road surface μ is equal to or less than the reaction force generation threshold μ (YES), it reads the area-specific camera-estimated road surface μ (step S28).

[0053] Thereafter, the vehicle integrated control unit 2 calculates the variation σμ of the camera-estimated road surface μc for each area divided and set on the image of one frame (step S29). Note that the processing in this step corresponds to the variation calculation unit of the present invention.

[0054] Then, the vehicle integrated control unit 2 compares the variation σμ of each area-specific camera-estimated road surface μc with a variation judgment threshold μth as a first threshold (step S30). This variation judgment threshold μth is used to determine whether the variation σμ of each area-specific camera-estimated road surface μc is large or not, and is a fixed value set in advance based on experiments or the like.

[0055] If the vehicle integrated control unit 2 determines that the variation σμ is small (σμ<μth) (step S30: NO), it sets the reaction force command value Fc for the pressure actuator 8 to the normal reaction force command value Fn (Fc←Fn: step S31). If the vehicle integrated control unit 2 determines that the variation σμ is large (σμ≧μth) (step S30: YES), it sets the reaction force command value Fc for the pressure actuator 8 to a reaction force command value Fh that is stronger than the normal reaction force command value Fn (Fc←Fh: step S32). If the electric vehicle M is predicted to travel on a road surface with a large variation σμ (μc≧σμ), increasing the reaction force command value Fc for the pressure actuator 8 allows the driver to respond more safely in the event of a slip. The processing in steps S30 to S32 corresponds to the reaction force command value setting unit of the present invention.

[0056] Thereafter, the vehicle integrated control unit 2 outputs a reaction force application command signal to apply the reaction force command value Fc to the pressure actuator 8 (step S33), and then exits the routine. Note that the processing in steps S28 to S33 corresponds to the reaction force instruction unit of the present invention. Also, the processing in step S33 corresponds to the reaction force command unit of the present invention.

[0057] The pressure actuator 8 applies a reaction force command value Fc to the accelerator pedal 31a and the brake pedal 31b in accordance with a reaction force command signal from the vehicle integrated control unit 2. This reaction force command value Fc is a force that repels the pressure applied when the driver depresses the accelerator pedal 31a and the brake pedal 31b. This reaction force may simply be a repulsive force applied to the accelerator pedal 31a and the brake pedal 31b. Alternatively, this reaction force may generate vibrations in the accelerator pedal 31a and the brake pedal 31b. Furthermore, this reaction force may simultaneously or alternately apply a repulsive force and vibrations to the accelerator pedal 31a and the brake pedal 31b.

[0058] As described above, according to this embodiment, since slip is detected from the slip vibration of the drive motor 14, it is possible to detect the occurrence of slip at an early stage and to notify the driver appropriately. Furthermore, when it is predicted that the electric vehicle M will travel on a road surface with a large variation σμ (μc≧σμ), the vehicle integrated control unit 2 increases the reaction force command value Fc for the pressure actuator 8, thereby enabling the driver to take measures in the event of slip more safely.

[0059] Furthermore, when the vehicle integrated control unit 2 detects that the driver is operating the steering wheel 31c when a slip occurs, the reaction force generation threshold μst is set to a high value μh, so that reaction forces can be applied to the accelerator pedal 31a and the brake pedal 31b at an early timing. This makes it possible to suppress the occurrence of a slip even if the driver's operation of the steering wheel 31c tends to exacerbate the occurrence of a slip.

[0060] The electric vehicle M may be a four-wheel drive vehicle. The estimated road surface μ initial setting routine shown in Fig. 2 may be executed by the vehicle integrated control unit 2. Furthermore, the slip suppression control may not only apply reaction forces to the accelerator pedal 31a and the brake pedal 31b, but may also notify the driver of the occurrence of slip by sound or an image on a monitor.

Claims

1. A vehicle control system comprising: a driving environment detection unit which detects the driving environment in front of an electric vehicle; a vibration detection unit which detects motor vibrations generated in the rotation speed of a drive motor mounted on the electric vehicle; a reaction force application unit which applies a reaction force to an operation unit operated by a driver; a region-by-region estimated road friction coefficient setting unit which estimates and sets a region-by-region road friction coefficient based on the driving environment information detected by the driving environment detection unit; a slip suppression control unit; and a reaction force instruction unit, wherein the slip suppression control unit comprises: a slip vibration detection unit which detects slip vibration from the motor vibration detected by the vibration detection unit; and a motor estimated road friction coefficient setting unit which, when the slip vibration is detected by the slip vibration detection unit, estimates and sets a road friction coefficient based on the slip vibration, and the reaction force instruction unit comprises: a variation calculation unit which calculates the variation in the region-by-region road friction coefficient detected by the region-by-region estimated road friction coefficient setting unit; a reaction force command value setting unit that compares the variation in road surface friction coefficient for each region calculated by the variation calculation unit with a first threshold value, and if the variation exceeds the first threshold value, sets a reaction force command value that generates a stronger reaction force than when the variation is below the first threshold value; and a reaction force command unit that outputs a command signal for the reaction force command value set by the reaction force command value setting unit to the reaction force application unit if the road surface friction coefficient set by the motor estimated road surface friction coefficient setting unit is equal to or lower than a second threshold value.

2. A control device for an electric vehicle as described in claim 1, further comprising a steering operation detection unit that detects steering operation by a driver, and the reaction force instruction unit further comprises a second threshold setting unit that, when the steering operation is detected by the steering operation detection unit, sets the second threshold to a higher value compared to when the steering operation is not detected.

3. The control device for an electric vehicle as described in claim 1, further comprising: a vehicle position detection unit that detects a current position of the electric vehicle; an environmental information acquisition unit that acquires surrounding environmental information of the electric vehicle based on the current position of the electric vehicle detected by the vehicle position detection unit; and an estimated road surface friction coefficient initial value setting unit that sets an initial value of an estimated road surface friction coefficient based on the surrounding environmental information acquired by the environmental information acquisition unit, wherein the area-specific estimated road surface friction coefficient setting unit corrects the estimated area-specific road surface friction coefficient with the initial value of the estimated road surface friction coefficient set by the estimated road surface friction coefficient initial value setting unit to set a new area-specific road surface friction coefficient.

4. The control device for an electric vehicle according to claim 3, wherein the surrounding environment information is at least one of road map information and weather information.

5. The control device for an electric vehicle according to claim 1, wherein the operation unit is at least one of an accelerator pedal and a brake pedal.

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