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
      Cruise Control Main Switch ON-OFF Button Turns the cruise control system on and off.
      MODE Switch A cancel signal can be output to the ECM when this switch is operated.
      CANCEL Switch A cancel signal can be output to the driving support ECU assembly through the operation of this switch.
      RES/+ Switch The accelerate function and resuming 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 decelerate function and vehicle speed setting resume signals are output to the driving support ECU assembly by operating this switch.
      Distance Control Switch While the system is in vehicle-to-vehicle distance control mode, the driver can operate the distance control switch to select the vehicle-to-vehicle distance in three stages: long, middle, and short.
      Stop Light Switch Assembly Detects the pressing of the brake pedal and transmits its signal to the driving support ECU assembly.
      Windshield Wiper Switch Assembly Transmits the windshield wiper switch assembly information to the driving support ECU assembly.
      Millimeter Wave Radar Sensor 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.
      Driving Support ECU Assembly

      • While the system is in the vehicle-to-vehicle distance control mode, the driving support ECU assembly detects the vehicle being followed based on signals from the millimeter wave radar sensor. Then, the driving support ECU assembly calculates the acceleration or deceleration rate required in order to attain the target vehicle-to-vehicle distance, and outputs a request signal to the power management control ECU and/or skid control ECU.

      • Controls the dynamic radar cruise control system in accordance with signals from the switches, sensors, skid control ECU and driving support ECU assembly.

      • If the driving support ECU assembly detects a malfunction in the cruise control system, it will store Diagnostic Trouble Codes (DTCs).
      Combination Meter Assembly Cruise Main Indicator Light Comes on when constant speed control mode is entered.
      Radar Cruise Control Indicator Light Comes on when the cruise main switch ON-OFF button is pressed to start the cruise control system.
      Master Warning Light Illuminates when there is a malfunction in the system.
      Buzzer If the power management control ECU or 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.
      Steering Angle Sensor (Spiral Cable with Sensor Sub-assembly) Detects the angle and direction of steering and transmits signals to the skid control ECU assembly and driving support ECU assembly.
      Yawrate Sensor Detects the yaw rate of the vehicle and transmits signals to the skid control ECU assembly and driving support ECU assembly.
      Rain Sensor This sensor detects raindrops, and when the wiper operates at HI speed, it requests the driving support ECU assembly to provide a cruise control cancel signal.
      Skid Control ECU While the system is operating in vehicle-to-vehicle distance control mode, the skid control ECU operates the brake actuator assembly in accordance with the brake request signal received from the driving support ECU assembly.
      Brake Actuator Assembly Applies the brakes in accordance with signals from the skid control ECU.
      Power Management Control ECU

      • Increases and decreases the motive force in accordance with the motive force request signals transmitted by the driving support ECU assembly.

      • Transmits the information about motive forces that are actually generated and can be generated to the driving support ECU assembly.
      ECM Actuates the throttle control motor in accordance with the signals from the power management control ECU.
      MG ECU Built into the inverter assembly. Controls the motive force of MG2 in accordance with signals from the power management control ECU.
      Headup Display Unit (Combination Meter Mirror ECU) Displays warning message on the windshield to inform or warn the driver of the system condition in accordance with signals from the driving support ECU assembly.
      Main Body ECU (Multiplex Network Body ECU) Transmits the SNOW signal to the power management control ECU.

  2. SYSTEM CONTROL


    1. The driving support ECU assembly, millimeter wave radar sensor, power management control ECU and ECM control this system.

    2. The combination meter assembly informs the driver of the control conditions.

    3. As in the radar cruise control system, the constant speed control mode is controlled by the driving support ECU assembly, which outputs signals to the power management control ECU.

      A019WECE01

    4. The vehicle-to-vehicle distance control mode is controlled by the millimeter wave radar sensor and driving support ECU assembly. Thus, the signals are output to the actuators and the ECU while exchanging data as indicated below.

      A019WAFE01

  3. FUNCTION


    1. The control of the dynamic radar cruise control system varies depending on the mode:


      • A: Constant Speed Control Mode

      • B: Vehicle-to-vehicle Distance Control Mode

        Function Outline Mode
        A B
        Constant Speed Control The driving support ECU assembly compares the actual vehicle speed and the set speed and if the vehicle speed is lower than the set speed, it regulates the drive force in order to accelerate the vehicle. ○ ○
        In constant speed control mode, constant speed control is performed by the driving support ECU assembly in the same way as conventional cruise control. ○ -
        In vehicle-to-vehicle distance control mode, constant speed control is performed by the millimeter wave radar sensor and driving support ECU assembly. - ○
        Deceleration Control Performs 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 performing deceleration control, the driver's own 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 if the vehicle ahead or the driver's own vehicle has changed lanes. - ○
        Set Control

        When the following conditions are met, and the cruise control switch is pressed to the -/SET side and released, the driving support ECU assembly stores the vehicle speed and maintains the vehicle constantly at the current speed.


        • The cruise control system is on.

        • The shift lever is in D or the shift lever is in S with 4th, 5th, or 6th shift range selected.

        		 ○ ○
        The vehicle is running at a speed of about 50 km/h (30 mph) or more. ○ ○
        The vehicle is driving at a speed between 50 and 170 km/h (30 and 106 mph). ○ ○
        Low Speed Limit Control The low speed limit is the lowest speed that cruise control can be set at and it is designed to be approximately 40 km/h (25 mph). The cruise control cannot be set below that speed. If the vehicle speed drops below that speed while driving using cruise control, the cruise control will be cancelled automatically. The vehicle set speed is kept in memory. ○ ○
        COAST Switch Control While the cruise control switch is held to the SET/- side, the vehicle speed and the vehicle set speed change as follows, according to the mode: ○ ○

        • The vehicle decelerates constantly.

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

        		 ○ -

        • The vehicle set speed decreases in increments of 5 km/h or 5 mph. [Example: 82 → 80 → 75 km/h (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 moved momentarily (approximately 0.6 seconds or less) to the -SET side, the vehicle speed and the set vehicle speed change as follows, according to the mode: ○ ○

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

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

        		 ○ -

        • The vehicle will decelerate in increments of approximately 5km/h or 5 mph each time the switch is moved.*1

        • The vehicle will decelerate in increments of approximately 1 km/h or 1 mph each time the switch is moved.*2

        		 - ○
        ACC Switch Control When the cruise control switch is held to the RES/+ side, the vehicle speed and the vehicle set speed change as follows, according to the mode: ○ ○

        • The vehicle will accelerate constantly.

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

        		 ○ -

        • The vehicle set speed increases in increments of 5 km/h or 5 mph. [Example: 62 → 65 → 70 km/h (mph)]

        • The vehicle will accelerate to the speed that is set at the time the switch is released. However, only the vehicle set speed will change during follow-up control.

        		 - ○
        RES Switch Control

        If the vehicle speed is above the low speed limit, the cruise control resumes operation (when the cruise control switch is subsequently pushed to the RES/+ side) to reach the vehicle speed that was set at the time the driver canceled cruise control.

        Even if the vehicle speed dropped below the low speed limit, the set speed can be resumed after the vehicle speed increases above the low speed limit.

        		 ○ ○
        Tap Up Control When the cruise control switch is moved momentarily (approximately 0.6 seconds or less) to the +RES side, the vehicle speed and the set vehicle speed change as follows: ○ ○

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

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

        		 ○ -

        • The vehicle will accelerate in increments of approximately 5 km/h or 5 mph each time the switch is moved.*1

        • The vehicle will accelerate in increments of approximately 1 km/h or 1 mph each time the switch is moved.*2

        		 - ○
        Manual Cancel Control

        If one of the following signals is sent to the driving support ECU assembly, the cruise control is cancelled accordingly.


        • Shift lever is moved from D to N.

        • When 1st, 2nd or 3rd shift range is selected manually while in S.

        • Stop light switch on signal/brake pedal depressed.

        • CANCEL switch on signal (cruise control switch moved to CANCEL side)

        • Cruise control main switch (ON-OFF button) off signal

        • HYBRID SNOW mode is selected.

        • VSC operation signal

        		 ○ ○
        Automatic Cancel Control When an automatic cancel signal is sent to the driving support ECU assembly, cruise control operation is canceled. At this time, the type of warning sent to the driver and the control resumption condition varies according to the cancel signal. ○ ○
        Mode Switching Control

        The following operations switch modes:


        • The ON-OFF button on the cruise control main switch is on. (Starts in the vehicle-to-vehicle distance control mode)

        • The cruise control switch is held to the MODE side. (for approximately 1 second or more). If the switch is pushed to any other side before switching modes, mode switching cannot be done. Push cruise control main switch (ON-OFF button) again.

        		 ○ ○
        Diagnosis If a malfunction occurs in the dynamic radar cruise control system during cruise control operation, the driving support ECU assembly cancels cruise control and memorizes information related to the malfunction. ○ ○

        Tech Tips

        ○: Available

        -: Not Available

        *1: Models for Europe

        *2: Models for G.C.C. Countries

    2. Constant Speed Control in Vehicle-to-Vehicle Distance Control


      1. The driving support ECU assembly compares the actual vehicle speed (wheel speed signal from the skid control ECU) with the set speed under constant speed control in each control mode. When the actual vehicle speed differs from the set speed, the driving support ECU assembly calculates the motive force required to achieve the set speed and transmits motive force request signals to the power management control ECU, thus controlling the motive force optimally and adjusting the vehicle speed to the set speed.

        A019WQ6E01

    3. Deceleration Control


      1. The driving support ECU assembly calculates the target deceleration rate in accordance with signals from the millimeter wave radar sensor, and transmits a deceleration request signal to the power management control ECU. Upon receiving this signal, the power management control ECU controls the motive force and decelerates the vehicle.

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

        A019W9FE01

      3. If the driving support ECU assembly determines that further deceleration is necessary, it transmits a motive force request signal to the skid control ECU. Upon receiving this signal, the skid control ECU then controls the brake actuator to apply the brakes.

      4. At this time, if the deceleration rate is higher than a predetermined value, the skid control ECU outputs a stop light illumination request signal to the stop light control relay, in order to warn any vehicles behind.

        A019WVWE01

      5. If the vehicle is not decelerating adequately, the driving support ECU assembly sounds a skid control buzzer assembly to prompt the driver to apply the brakes.

        A019WUNE01

    4. Follow-up Control


      1. After performing deceleration control, the driving support ECU assembly transmits a motive force request signal to the power management control ECU so that the vehicle can follow the vehicle ahead while maintaining the proper vehicle-to-vehicle distance according to the preceding vehicle's speed. Upon receiving this signal, the power management control ECU controls the motive force in order to effect follow-up control.

      2. 3 stages (long, middle, and short) of vehicle-to-vehicle distance can be selected by operating the distance control switch.

        A019WA8E01

    5. Acceleration Control

      If the driving support ECU assembly detects (based on the millimeter wave radar sensor) that either the vehicle ahead or own vehicle has changed lanes, an acceleration request signal is transmitted to the power management control ECU in order to attain the set vehicle speed. Upon receiving this signal, the power management control ECU controls the motive force of the engine and MG2 in order to perform acceleration control.

      A019WQVE01

    6. Automatic Cancel Control

      If one of the conditions listed below occurs 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.


      1. Warning message is displayed on the multi-information display.

      2. Master warning light.

      3. Buzzer sounds.

        Constant Speed Control Mode:
        Description of Malfunction Warning

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


        • Malfunction of the vehicle speed signal (SPD).

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

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

        1. "CHECK CRUISE CONTROL SYSTEM"

        2. Illuminates

        3. Sounds once

        If the following condition 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 [approximately 40 km/h (25 mph)].

        1. -

        2. -

        3. -

        If the following condition 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.

        1. -

        2. -

        3. -
        Vehicle-to-Vehicle Distance Control Mode:
        Description of Malfunction Warning

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


        • Malfunction of the vehicle speed signal (SPD).

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

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

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

        1. "CHECK CRUISE CONTROL SYSTEM"

        2. Illuminates

        3. Sounds once

        If the following condition 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 [approximately 40 km/h (25 mph)].

        1. -

        2. -

        3. -

        If one of the following conditions occurs, the driving support ECU assembly clears the set vehicle speed and cancels the cruise control.


        • Malfunction of the millimeter wave radar sensor.

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

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

        The cruise control system will be disabled until the next time the power switch is turned on (IG).

        1. "CHECK CRUISE CONTROL SYSTEM"

        2. Illuminates

        3. Sounds once

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


        • The millimeter wave radar sensor is dirty.

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

        1. "CLEAN RADAR SENSOR"

        2. Illuminates

        3. Sounds once

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


        • The wipers operate at HI speed (including AUTO mode).

        • SNOW mode is selected.

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

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

        1. "CRUISE CONTROL NOT AVAILABLE"

        2. Illuminates

        3. Sounds once

  4. CONSTRUCTION


    1. Cruise Control Main Switch


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

      2. The cruise control 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.

        A019WNBE01
        *1 Cruise Control Main Switch *2 ON/OFF Button
        *a ON/OFF *b +/RES
        *c MODE *d -/SET
        *e CANCEL - -

    2. Distance Control Switch


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

        A019WCFE01
        *1 Distance Control Switch - -

      2. If the power 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 Approximately 50 m (165 ft.)
        Middle Approximately 40 m (125 ft.)
        Short Approximately 25 m (80 ft.)

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

    3. Millimeter Wave Radar Sensor


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

      2. The millimeter wave radar circuit consists of one transmission antenna and 5 reception antennas.

      3. 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 GHz band.

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

      5. 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 assembly.

        A019WH6E02

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

        Distance Calculate 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.
        Azimuth Calculated from the angle of the waves reflected by the millimeter wave radar that have been received.
        Relative Speed Calculated by utilizing the changes (Doppler effect*) that occur in the frequencies of the reflected millimeter wave radar waves.

        • *: The Doppler effect causes the observer to perceive the radio wave emitted by a moving object to be of higher frequencies as it approaches, and to be of lower frequencies as it recedes. This phenomenon is created because when an object is located far away, the radio waves are perceived at higher frequencies than those of the radio source.

          A019WOBE01

  5. OPERATION


    1. Combination Meter Assembly


      1. The combination meter assembly uses a master warning light, cruise main indicator light, buzzer, headup display and multi-information display to provide the driver with dynamic radar cruise control system warnings and indications.

      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, headup display or multi-information display.

        Mode Condition Multi-information Display Cruise Main Indicator Light Master Warning Light Buzzer
        Constant Speed Control Being Controlled A019WIU Illuminates - -
        Vehicle-to-Vehicle Distance Control Set Standby A019WEH Illuminates - -
        Under Constant Speed Control (No Vehicle Ahead) A019WCME01 Illuminates - -
        Under Follow-up Control (Vehicle Ahead) A019WNOE01 Illuminates - -
        Deceleration Control/ Vehicle Approach Warning (Vehicle Ahead)*1 A019WE3E01 Illuminates - -
        System Failure Millimeter wave radar sensor is dirty. A019WDG - Illuminates Sounds once
        Poor Weather Condition A019WF8 - Illuminates Sounds once
        System Check*2 A019WMS - Illuminates Sounds once
        Beam Axis Adjustment A019WH4 - - -

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

        • *2: When a Diagnostic Trouble Code (DTC) is memorized.

  6. DIAGNOSIS


    1. If a malfunction occurs in the dynamic radar cruise control system during cruise control operation, the driving support ECU automatically cancels the cruise control, illuminates the master warning light, sounds a buzzer and displays "CHECK CRUISE CONTROL SYSTEM" on the multi-information display to inform the driver of the malfunction. At this time, the malfunction is stored in memory as Diagnostic Trouble Codes (DTCs).

    2. DTCs can be read when a intelligent tester is connected to the DLC3.

    3. The intelligent tester can be used to read the 5-digit codes.