DYNAMIC RADAR CRUISE CONTROL SYSTEM DETAILS


  1. FUNCTION OF MAIN COMPONENTS


    1. The main components in the dynamic radar cruise control system have the following functions:

      Component Function
      Millimeter Wave Radar Sensor Assembly Radiates millimeter radar waves forward, uses the reflected waves to detect the presence of a vehicle being driven ahead, the vehicle-to-vehicle distance and the relative speed, and then transmits this information to the driving support ECU assembly.
      Cruise Control Main Switch ON-OFF Button Turns the cruise control system on and off.
      MODE Switch Switches between the constant speed control mode and vehicle-to-vehicle distance control mode.
      CANCEL Switch A cancel signal can be output to the driving support ECU assembly through the operation of this switch.
      +RES Switch The acceleration function and resumption of a preset speed can be performed by operating this switch. A signal is output to the driving support ECU assembly when this switch is operated.
      -SET Switch The deceleration function and vehicle speed setting resume signals are output to the driving support ECU assembly due to operation of this switch.
      Distance Control Switch While the system is in the vehicle-to-vehicle distance control mode, the driver can operate the distance control switch to select the vehicle-to-vehicle distance in 3 stages: long, middle, and short.
      Driving Support ECU Assembly

      • Calculates the acceleration or deceleration required to achieve the target vehicle speed/target vehicle-to-vehicle distance based on signals from switches, sensors and ECUs and transmits acceleration or deceleration request signals to the ECM (to accelerate the vehicle) and/or the skid control ECU (to decelerate the vehicle).

      • Determines the presence of a preceding vehicle based on information from the millimeter wave radar sensor assembly.

      • Transmits control status display request signals, warning display request signals and diagnosis signals for the dynamic radar cruise control system.
      ECM

      • Actuates the throttle control motor in accordance with the signals from the driving support ECU assembly.
      Skid Control ECU Assembly

      • While the system is operating in vehicle-to-vehicle distance control mode, the skid control ECU assembly performs brake control in accordance with request signals from the driving support ECU assembly.

      • Transmits signals such as wheel speed and estimated vehicle acceleration to the driving support ECU assembly.
      Combination Meter Assembly Cruise Control Main Indicator Light

      • Comes on when constant speed control mode is entered.

      • Turns off if a malfunction occurs during constant speed control mode control.
      Radar Cruise Control Indicator Light

      • Comes on when the cruise control main switch ON-OFF button is pressed to start the cruise control system.

      • Turns off if a malfunction occurs during vehicle-to-vehicle distance control mode control.
      Cruise Control SET Indicator Light Illuminates when the vehicle speed is set during cruise control driving.
      Master Warning Light Illuminates when there is a malfunction in the system.
      Multi Buzzer When the driving support ECU assembly detects automatic cancel or warning signals while the vehicle is operating under cruise control, this buzzer sounds to inform the driver.
      Multi-information Display During dynamic radar cruise control operation, the multi-information display receives signals from the driving support ECU assembly in order to display the system conditions.
      Combination Meter Mirror ECU During vehicle approach warning operation, the head up display receives signals from the combination meter assembly in order to display the warning conditions.
      Throttle Control Motor Adjusts the throttle valve opening angle in accordance with signals from the ECM.
      Brake Actuator Assembly Actuates the brakes in accordance with the signals from the skid control ECU assembly.
      Integration Relay Illuminates the stop light in accordance with the stop light illumination request signal from the skid control ECU assembly.
      Skid Control Buzzer Assembly Sounds on receiving a signal from the skid control ECU assembly and alerts the driver that the distance between the vehicles is short.
      Speed Sensor Detects the wheel speed of each of the 4 wheels.
      Accelerator Pedal Sensor Assembly Detects the accelerator pedal depression degree and outputs it to the ECM.
      Park/Neutral Start Switch Assembly Detects the shift position and transmits signals to the ECM.
      Steering Sensor Detects the angle and direction of steering and transmits signals to the driving support ECU assembly.
      Yawrate Sensor Detects the yaw rate of the vehicle and transmits signals to the driving support ECU assembly.
      Stop Light Switch Assembly Detects the pressing of the brake pedal and transmits its signal to the driving support ECU assembly and skid control ECU assembly.

  2. FUNCTION


    1. Control of Dynamic Radar Cruise Control System Varies Depending on Mode


      • A: Constant speed control mode

      • B: Vehicle-to-vehicle distance control mode

      Function Outline Mode
      A B
      Constant Speed Control The ECM compares the actual vehicle speed and the set speed. When the vehicle speed is higher than the set speed, it uses the throttle control motor to decrease the throttle opening. When the actual vehicle speed is lower than the set speed, it uses the throttle control motor to increase the throttle opening. ○ ○
      Deceleration Control Effects throttle control and brake control in order to decelerate the vehicle so that the vehicle-to-vehicle distance between the driver's own vehicle and the vehicle ahead equals the set distance. - ○
      Follow-up Control After effecting deceleration control, the vehicle follows the vehicle ahead in order to maintain the proper vehicle-to-vehicle distance in accordance with the vehicle speed. - ○
      Acceleration Control Accelerates the vehicle in order to attain the set vehicle speed when the vehicle or the vehicle ahead has changed lanes. - ○
      Set Control

      While this system fulfils the following condition and the cruise control switch is pressed to the -SET direction and released when the main switch on the cruise control switch has been pressed to turn the system on, the ECM stores the vehicle speed and maintains the vehicle constantly at that speed.


      • The shift lever is in D.

      		 ○ ○

      The vehicle is running within the following speed range:


      • Approx. 50 km/h to 200 km/h (30 mph to 125 mph)

      		 ○ -

      The vehicle is running within the following speed range:


      • Approx. 50 km/h to 170 km/h (30 mph to 105 mph)

      		 - ○
      Low Speed Limit Control The low speed limit is the lowest speed that the dynamic radar cruise control system can be set at and it is designed to be approx. 40 km/h (25 mph). The cruise control system cannot be set below this speed. If the vehicle speed drops below this speed while the cruise control system is running, the cruise control system will be canceled automatically. However, the set speed is kept in the memory. ○ ○
      Coast Control While the cruise control switch is held to the -SET direction, the vehicle speed and the set speed change as follows, in accordance with the mode: ○ ○

      • The vehicle decelerates constantly

      • The set speed changes to the speed at which the switch is released.

      		 ○ -

      • The set speed decreases in increments of 5 km/h or 5 mph (example: 57 → 55 → 50 km/h, 57 → 55 → 50 mph).

      • The vehicle will remain at the speed that the vehicle is traveling at when the coast switch is released.

      		 - ○
      Tap-down Control When the cruise control switch is pushed momentarily (approx. 0.6 seconds or less) to the -SET direction, the vehicle speed and the set speed change as follows, in accordance with the mode: ○ ○

      • The vehicle will decelerate in increments of approx. 1.6 km/h (1mph) each time the switch is pressed.

      • However, if the difference between the actual vehicle speed and the set speed is greater than 5 km/h (3 mph), the set speed will change to the speed at which the vehicle was being driven at the time the switch was operated.

      		 ○ -
      When the cruise control switch is pushed momentarily (approx. 0.6 seconds or less) to the -SET direction, the vehicle will decelerate in increments of approx. 1 km/h or 1 mph each time the switch is pressed. - ○
      Accelerator Control When the cruise control switch is pushed to the +RES direction and held, the vehicle speed and the set speed change as follows, in accordance with the mode: ○ ○

      • The vehicle will accelerate constantly.

      • The set speed changes to the speed at which the switch is released.

      		 ○ -

      • The set speed increases in increments of 5 km/h or 5 mph (example: 52 → 55 → 60 km/h, 52 → 55 → 60 mph).

      • The vehicle will accelerate to the speed that is set at the time the switch is released.

      • However, only the set speed will change during follow-up control.

      		 - ○
      Tap-up Control When the cruise control switch is pushed momentarily (approx. 0.6 seconds or less) to the +RES direction, the vehicle speed and the set speed change as follows: ○ ○

      • The vehicle will accelerate in increments of approx. 1.6 km/h (1 mph) each time the switch is pressed.

      • However, if the difference between the actual vehicle speed and the set speed is greater than 5 km/h (3 mph), the set speed does not change.

      		 ○ -
      The vehicle will accelerate in increments of approx. 1 km/h or 1 mph each time the switch is pressed. - ○
      Resume Control When the vehicle speed is above the low speed limit, the cruise control resumes operation (when the cruise control main switch is subsequently moved to the +RES side) to reach the vehicle speed that was set at the time the driver canceled cruise control. ○ ○
      When the vehicle ahead changes driving lanes during follow-up control, the vehicle speed is gradually increased to the set speed. At this time, the vehicle speed can be increased promptly by pushing the cruise control switch to the +RES direction. - ○
      Shift Down Control When the vehicle is traveling uphill using cruise control, automatic transmission control may cause the transmission to shift down. During shift down control, when the end of uphill travel is determined, the transmission will shift up after a certain period of time. When the transmission shifts down during the accelerator control or the resume control, the transmission will shift up after the accelerator control or the resume control ends. ○ ○
      Manual Cancel Control

      When any of the following signals are sent to the driving support ECU assembly, the dynamic radar cruise control system is canceled accordingly:


      • Stop light switch on signal (the brake pedal is depressed).

      • D position off signal (the shift lever is moved from D to N).

      • Signal to select the D1, D2 and D3 ranges in D position by paddle shift control.

      • Signal to select the M1, M2 and M3 ranges

      • CANCEL switch on signal (the cruise control switch is moved to the CANCEL direction).

      • Main switch off signal.

      		 ○ ○
      Automatic Cancel Control When an automatic cancel signal is sent to the driving support ECU assembly, the cruise control system operation is canceled. At this time, the warning method and the control resumption condition vary in accordance with the cancel signal. ○ ○
      Mode Switching Control

      The following operations switch the modes:


      • (a) Main switch on the cruise control switch is on (starts in the vehicle-to-vehicle distance control mode).

      • (b) Cruise control switch is held to the MODE direction (approx. 1 second or more).

      If the switch is pushed in any other direction before switching modes, switch the dynamic radar cruise control system is turned off, then perform steps (a) and (b) again.

      		 ○ ○

      Tech Tips

      ○: Available

      -: Not available

    2. Constant Speed Control Function in Vehicle-to-vehicle Distance Control Mode


      1. The millimeter wave radar sensor assembly transmits the information about the vehicle ahead to the driving support ECU assembly. The driving support ECU assembly transmits this signal to the ECM.

      2. The ECM compares the set speed and the actual vehicle speed, and effects constant speed control by regulating the throttle control in order to attain the set speed.

        A01FBLRE01

    3. Deceleration Control Function


      1. The driving support ECU assembly calculates the target deceleration rate in accordance with signals from the millimeter wave radar sensor assembly, and transmits a deceleration request signal to the ECM.

      2. The ECM closes the throttle valve upon receiving this signal in order to cause the vehicle to decelerate.

      3. This control is not effected in the presence of a parked vehicle or object, or below the settable vehicle speed range.

        A01FC9NE01

      4. When the driving support ECU assembly determines that further deceleration is necessary, it transmits a brake request signal to the ECM. Upon receiving this signal, the ECM transmits a brake request signal to the skid control ECU assembly. The skid control ECU assembly then controls the brake actuator assembly to apply the brakes.

        A01FC75E01

      5. When further deceleration is necessary, the skid control ECU assembly sounds the skid control buzzer assembly based on the request signal from the driving support ECU assembly to urge the driver to depress the brake pedal.

        A01FBNXE01

    4. Follow-up Control Function


      1. After effecting deceleration control, the driving support ECU assembly transmits a request signal to the ECM so that the vehicle can follow the vehicle ahead while maintaining the proper vehicle-to-vehicle distance in accordance with the vehicle speed.

      2. The ECM regulates the throttle upon receiving this signal in order to effect follow-up control.

      3. 3 stages (long, middle and short) of vehicle-to-vehicle distance can be selected by operating the distance control switch.

        A01FBXEE01

    5. Acceleration Control Function


      1. When the driving support ECU assembly detects (based on the millimeter wave radar sensor assembly) that either the vehicle or the vehicle ahead has changed lanes, an acceleration request signal is transmitted to the ECM in order to attain the set vehicle speed.

      2. The ECM regulates the throttle upon receiving this signal in order to effect acceleration control.

        A01FBS5E01

    6. Automatic Cancel Control


      1. When any of the conditions listed below occur while the vehicle is being driven using cruise control, the cruise control will be canceled. Then, the following warning items will appear for the driver.

        Constant Speed Control Mode
        Description of Malfunction Warning
        Multi-information Display Master Warning Light Multi Buzzer Cruise Control Main Indicator Light

        If the conditions listed below occur, the driving support ECU assembly clears the set vehicle speed and cancels the cruise control.


        • Millimeter wave radar sensor assembly and driving support ECU assembly region code mismatch is detected.

        • Malfunction of the vehicle speed signal

        • An open or short circuit in the stop light switch assembly

        The cruise control is prohibited until the conditions are remedied or the cruise control system is turned off and back on again using the ON-OFF button on the cruise control main switch.

        		 Check Cruise Control System Illuminates Sounds Once -

        If the condition listed below occur, the driving support ECU assembly clears the set vehicle speed and cancels the cruise control.


        • Malfunction in the throttle control system

        The cruise control is prohibited until the conditions are remedied or the cruise control system is turned off and back on again using the ON-OFF button on the cruise control main switch.

        		 - - - -

        If the condition listed below occurs, the driving support ECU assembly clears the set vehicle speed and cancels the cruise control.


        • The vehicle speed drops more than 16 km/h (10 mph) below the set vehicle speed.

        		 - - - -

        If the conditions listed below occurs, the driving support ECU assembly cancels the cruise control while retaining the set vehicle speed in its memory.


        • The VSC system operates.

        • The TRC system operates for some time.

        • The VSC or TRC is in OFF mode.

        		 - - - -

        If the conditions listed below occur, the driving support ECU assembly clears the set vehicle speed and cancels the cruise control.


        • Malfunction of the cancel circuit

        • Malfunction of the stop light switch assembly input signal circuit

        The cruise control is prohibited until the engine switch is turned on again.

        		 Check Cruise Control System Illuminates Sounds Once -
        Vehicle-to-vehicle Distance Control Mode
        Description of Malfunction Warning
        Multi-information Display Master Warning Light Multi Buzzer Cruise Control Main Indicator Light

        If any of the conditions listed below occurs, the driving support ECU assembly clears the set vehicle speed and cancels the cruise control.


        • Millimeter wave radar sensor and driving support ECU region code mismatch is detected.

        • Malfunction of the vehicle speed signal

        • An open or short circuit in the stop light switch assembly

        The cruise control is prohibited until the conditions are remedied or the cruise control system is turned off and back on again using the ON-OFF button on the cruise control main switch.

        		 Check Cruise Control System Illuminates Sounds Once -

        If the condition listed below occur, the driving support ECU assembly clears the set vehicle speed and cancels the cruise control.


        • Malfunction in the throttle control system

        The cruise control is prohibited until the conditions are remedied or the cruise control system is turned off and back on again using the ON-OFF button on the cruise control main switch.

        		 - - - -

        If the condition listed below occurs, the driving support ECU assembly clears the set vehicle speed and cancels the cruise control.


        • Malfunction of the millimeter wave radar sensor assembly

        • Displacement of the axis of the millimeter wave radar sensor assembly

        • Malfunction in the dynamic radar cruise control system other than those given above.

        The cruise control is prohibited until the engine switch is turned on again.

        		 Check Cruise Control System Illuminates Sounds Once -

        If the condition listed below occurs, the driving support ECU assembly cancels the cruise control while retaining the set vehicle speed in its memory.


        • The millimeter wave radar sensor assembly is dirty.

        The cruise control is prohibited until the conditions are remedied or the cruise control system is turned off and back on again using the ON-OFF button on the cruise control main switch.

        		 Clean Radar Sensor Illuminates Sounds Once -

        If any of the conditions listed below occur, the driving support ECU assembly cancels the cruise control while retaining the set vehicle speed in its memory.


        • The wipers operate at high speed.

        • The measurement becomes extremely unstable due to poor weather conditions.

        The cruise control is prohibited until the conditions are remedied or the cruise control system is turned off and back on again using the ON-OFF button on the cruise control main switch.

        		 Cruise Control not available Illuminates Sounds Once -

        If the conditions listed below occurs, the driving support ECU assembly cancels the cruise control while retaining the set vehicle speed in its memory.


        • The vehicle speed drops below low speed limit (approx. 40 km/h [25 mph]).

        • The VSC system operates.

        • The TRC system operates for a certain period time.

        • The VSC or TRC is in OFF mode.*

        		 - - Sounds Twice -

        If the condition listed below occurs, the driving support ECU assembly clears the set vehicle speed and cancels the cruise control.


        • The vehicle speed drops more than 16 km/h (10 mph) below the set vehicle speed.

        		 - - - -

        If the conditions listed below occur, the driving support ECU assembly clears the set vehicle speed and cancels the cruise control.


        • Malfunction of the cancel circuit

        • Malfunction of the stop light switch assembly input signal circuit

        The cruise control is prohibited until the engine switch is turned on again.

        		 Check Cruise Control System Illuminates Sounds Once -

        Tech Tips

        *: Multi buzzer not sounds

  3. CONSTRUCTION


    1. Cruise Control Main Switch


      1. The cruise control main switch consists of the ON-OFF button, +RES, MODE, -SET and CANCEL switches. The +RES, MODE, -SET and CANCEL switches are operated by moving the lever in the 4 directions indicated.

      2. The cruise control main switch is an automatic reset (normally open) type that turns on only when the switch is being operated and turns off as soon as the driver releases the switch. Furthermore, the functions of the control switch are active only when the cruise control system has been turned on using the ON-OFF button on the cruise control main switch.

        A01FBVPE01
        Text in Illustration
        *1 Cruise Control Main Switch - -
        *a ON-OFF Button *b +RES Switch
        *c MODE Switch *d -SET Switch
        *e CANCEL Switch - -

    2. Distance Control Switch


      1. While the vehicle is being driven in vehicle-to-vehicle distance control mode, the vehicle-to-vehicle distance setting changes as follows each time the distance control switch is pressed; long → middle → short.

        A01FCA3E01
        Text in Illustration
        *1 Distance Control Switch - -

      2. If the engine switch is turned off and back to on (IG), the system will default to "long".

      3. The vehicle-to-vehicle distance is set as follows:

        Mode Vehicle-to-vehicle Distance*
        Long Approx. 50 m (160 ft.)
        Middle Approx. 40 m (130 ft.)
        Short Approx. 30 m (100 ft.)

        Tech Tips

        *: While driving at a vehicle speed of 80 km/h (50 mph).

    3. Millimeter Wave Radar Sensor Assembly


      1. The millimeter wave radar sensor assembly consists of a millimeter wave radar circuit, signal processing circuit, and CPU.

      2. The millimeter wave radar outputs waves when the vehicle speed is above 0 km/h (0 mph), and not when the vehicle speed is at 0 km/h (0 mph). The millimeter wave radar uses frequencies in the 76.5 GHz band.

      3. The reception antennas receive the millimeter wave radar waves that have been reflected.

      4. The signal processing circuit detects the distance, relative speed, and the direction of the object by generating millimeter wave radar waves and calculating the signals received by the reception antennas. Then, it transmits this information to the driving support ECU.

        A01FC3AE01
        Text in Illustration
        *1 Millimeter Wave Radar Sensor Assembly - -
        *a Detection Distance: Approx. 150 m (490 ft.) *b Horizontal Angle: Approx. 20°
        *c Vertical Angle: Approx. 8° *d Signal Processing Circuit
        *e Millimeter Wave Radar Circuit - -

      5. The distance to the object, azimuth and relative speed are calculated from the information that is provided by the reflection millimeter wave radar as described below.

        Item Calculation Method
        Distance Calculated from the length of time that has elapsed from the time the waves of the millimeter wave radar have been emitted, until the waves reflected by the millimeter wave radar are received. The detection distance is approx. 150 m (490 ft.).
        Azimuth Calculated from the angle of the waves reflected by the millimeter wave radar that have been received. The detection angle has a horizontal angle of approx. 20° and a vertical angle of approx. 8°.
        Relative Speed Calculated by utilizing the changes (Doppler effect*) that occur in the frequencies of the reflected millimeter wave radar waves.

        Tech Tips

        *: The Doppler effect causes the observer to perceive the radio waves emitted by a moving object to be of higher frequencies as it approaches, and to be of lower frequencies at it recedes.

        A01FC8DE01

        Tech Tips

        An SST is used if radar axis adjustment is needed. For details, refer to the Repair Manual.

  4. OPERATION


    1. Combination Meter Assembly


      1. The combination meter assembly provides a master warning light, cruise main indicator light, radar cruise control indicator light, cruise SET indicator light, multi buzzer, and multi-information display to provide warnings and messages regarding the dynamic radar cruise control system.

      2. The multi-information display displays the set vehicle speed, vehicle ahead mark, and warning message.

      3. Examples are shown below for the illumination or display of each indicator light, warning light or multi-information display:

        Constant Speed Control Mode
        Condition Multi-information Display Cruise Control Main Indicator Light Cruise Control SET Indicator Light Master Warning Light Multi Buzzer
        Being Controlled A01FBL2 Illuminates Illuminates - -
        System Check A01FBM6 - - Illuminates Sounds once
        Vehicle-to-vehicle Distance Control Mode
        Condition Multi-information Display*1 Radar Cruise Control Indicator Light Cruise Control SET Indicator Light Master Warning Light Multi Buzzer
        Set Standby A01FC9W Illuminates - - -
        Under Constant Speed Control (No Vehicle Ahead) A01FBVFE01 Illuminates Illuminates - -
        Under Follow-up Control (Vehicle Ahead) A01FCDFE01 Illuminates Illuminates - -
        Under Brake Control (Vehicle Ahead) A01FBXDE01 Illuminates Illuminates - -
        Deceleration Control/Vehicle Approach Warning (Vehicle Ahead, Long)*2 A01FCBBE01 Illuminates Illuminates - Skid Control Buzzer Sounds Continuously
        Millimeter Wave Radar Sensor is Dirty A01FC0I - - Illuminates Sounds Once
        Poor Weather Conditions*3 A01FBSV - - Illuminates Sounds Once
        System Check A01FBM6 - - Illuminates Sounds Once
        Beam Axis Adjustment A01FBXN - - - -

        Tech Tips

        *1: When the lane-keeping assist system is operating, its indicator is also displayed. For details, refer to lane-keeping assist system.

        *2: Displayed on the headup display also for vehicles with the headup display.

        *3: When the wipers operate at high speed or the ECT is selected at snow mode.