Dynamic Radar Cruise Control System System Description

Cruise Control System. Lexus Gs430, Gs300. Uzs190 Grs190
Cruise Control. Lexus Gs430, Gs300. Uzs190 Grs190

  1. GENERAL

  1. FUNCTION OF MAIN COMPONENTS

  1. LIMIT CONTROL

  1. CRUISE CONTROL OPERATION

  1. BRAKE CONTROL

  1. DOWNSHIFT CONTROL

  1. AUTO CANCEL (FAIL-SAFE)

Dynamic Radar Cruise Control System -- System Description



GENERAL

  1. The dynamic radar cruise control system has two cruise control modes: the constant speed control mode and vehicle-to-vehicle distance control mode.

    1. The vehicle-to-vehicle distance control mode is always selected when starting the dynamic radar cruise control system.
    2. Operation of the constant speed control mode is the same as that for a conventional cruise control system.

  2. This system maintains the vehicle running at the speed that the driver has set, as long as there are no vehicles ahead in the same lane. Then, the system maintains the vehicle distance that has been set by the driver. If the system detects a vehicle driving at a slower speed ahead while the driver is driving at a constant speed, it closes the throttle valve to decelerate. If further deceleration is required, the system controls the brake actuator in order to apply the brakes. Thereafter, if there are no vehicles ahead within the set vehicle-to-vehicle distance because either the vehicle ahead or the driver has changed lanes, the system accelerates slowly to reach the set vehicle speed and resumes driving at the constant speed.

  3. The constant speed control mode is designed to maintain a constant cruising speed. The vehicle-to-vehicle distance control mode is designed to control cruising using a constant speed function, deceleration cruising function, follow-up cruising function and acceleration cruising function.

  4. The millimeter wave radar sensor and distance control ECU (cruise control ECU) control the system while the vehicle-to-vehicle distance control mode is in operation, and send signals to each actuator and ECU.

  5. In vehicle-to-vehicle distance control mode, the dynamic radar cruise control system receives signals from the yaw rate (deceleration sensor) and the steering angle sensors. Based on these signals, it then estimates curve radius and compensates for information on the preceding vehicle while turning. It can also compensate for the brake control when approaching another vehicle.

  6. This system judges the presence of a vehicle in front and the distance to it based on the signals from the radar sensor while the vehicle-to-vehicle distance control mode is in operation. Using this information, the system informs the driver of any danger with the warning buzzer, performs brake control, and illuminates the stop lights when approaching the vehicle in front.



  7. The following illustration shows a control example under the following conditions: own vehicle speed is 100 km/h (62 mph) and the speed of the vehicle in front is 80 km/h (50 mph). Setting of the vehicle distance can be changed to 3 distances by operating the distance control switch (distance control switch): long (approximately 75 m (246 ft)), middle (approximately 50 m (164 ft)), and short (approximately 30 m (98 ft)) when the vehicle speed is approximately 90 km/h (55 mph).


    Lexus Gs430, Gs300. Uzs190 Grs190.Cruise Control.Cruise Control System.Dynamic Radar Cruise Control System System Description

    HINT:
    1. Vehicle distance increases and decreases in accordance with vehicle speed.
    2. Controlling condition is indicated on the multi-information display in the combination meter.

FUNCTION OF MAIN COMPONENTS

Item
Outline
Combination Meter (CRUISE Main Indicator Light)
  1. Comes on when main switch is ON
  2. If distance control ECU detects malfunction, this light flashes to warn driver
Combination Meter (Master Warning Light)
If ECM or distance control ECU detects automatic cancel signal while vehicle is operating under cruise control, this light comes on to inform driver
Combination Meter (Buzzer)
If ECM or distance control ECU detects automatic cancel signal while vehicle is operating under cruise control, this buzzer sounds only once to inform driver
Combination Meter (Multi-information Display)
  1. While system is in vehicle-to-vehicle distance control mode, multi-information display receives signals from distance control ECU, in order to display system conditions in graphic area
  2. If ECM or distance control ECU detects malfunction signal while vehicle is operating under cruise control, warning message will be displayed in warning area to inform driver
  3. While system is in radar sensor adjustment mode, adjustment angle detected by distance control ECU will be displayed in warning area to inform driver
Cruise Control Main Switch (Main Switch)
Turns cruise control system ON/OFF
Cruise Control Main Switch (Control Switch)
  1. Vehicle speed setting, deceleration setting, preset speed resumption, acceleration setting, and canceling signals are output to ECM through operation of this switch
  2. Switches control mode: constant speed control mode and vehicle-to-vehicle distance mode
Steering Pad Switch (Distance Control Switch)
While system is in vehicle-to-vehicle distance control mode, driver can operate steering pad switch (distance control switch) to select vehicle-to-vehicle distance in three stages: long, middle, and short
Stop Light Switch
Detects pressing of brake pedal and transmits its signal to ECM
Combination Switch
(Wiper Switch)
Transmits wiper control switch information to distance control ECU
Millimeter Wave Radar Sensor
Radiates radar waves forward, uses reflected waves for detecting presence of vehicle in front, vehicle-to-vehicle distance, and relative speed, and transmits this information to distance control ECU
Steering Angle Sensor
Detects angle and direction of steering and transmits its signal to distance control ECU
Vehicle Speed Sensor (SP1)
Vehicle speed signal which is output from skid control ECU is sent to ECM via meter
Yaw Rate Sensor
Detects yaw rate of vehicle and transmits its signal to distance control ECU
Rain Sensor
This sensor detects raindrops, and when wiper operates at LO or HI, it requests distance control ECU to transmit cruise control cancel signal
Brake Actuator (Skid Control ECU)
  1. Actuates brakes in accordance with signals from skid control ECU
  2. While system is in vehicle-to-vehicle distance control mode, skid control ECU actuates brake actuator in accordance with brake request signal received from distance control ECU
  3. Upon receiving signal from distance control ECU, skid control ECU sounds skid control buzzer
Skid Control Buzzer
This buzzer sounds upon receiving signal from skid control ECU
ECM
  1. Controls dynamic radar cruise control system in accordance with signals from switches, sensors, and distance control ECU
  2. If ECM detects malfunction in dynamic radar cruise control system, it will output DTCs (Diagnostic Trouble Codes)
Throttle Position Sensor and Motor
Upon receiving signal from ECM, throttle control motor actuates throttle valve
Distance Control ECU
(Cruise Control ECU)
While system is in vehicle-to-vehicle distance control mode, distance control ECU detects vehicle in front based on signal from millimeter wave radar sensor. Then, distance control ECU calculates acceleration or deceleration rate in order to attain target vehicle-to-vehicle distance, and outputs request signal to ECM and skid control ECU

LIMIT CONTROL

  1. Low speed limit
    The lowest possible limit of the speed setting range is approximately 43 km/h (27 mph). The cruise control system cannot be set when the driving vehicle speed is below the low speed limit. Cruise control operation will be automatically canceled and the stored vehicle speed will be erased when the vehicle speed decreases below the low speed limit (40 km/h (25 mph)) while the cruise control is in operation.

  2. High speed limit (constant speed control mode)
    The highest possible limit of the speed setting range is approximately 200 km/h (125 mph). The cruise control system cannot be set when the driving vehicle speed is over the high speed limit. Also, RESUME / ACCEL cannot be used to increase speed beyond the high speed limit.

  3. High speed limit (vehicle-to-vehicle distance control mode)
    The highest possible limit of the speed setting range is approximately 106 mph (Europe) and 139 km/h (Australia).


CRUISE CONTROL OPERATION
The cruise control main switch operates 8 functions: SET, COAST, TAP-DOWN, RESUME, ACCEL, TAP-UP, CANCEL, and MODE. The SET, TAP-DOWN and COAST functions, and the RESUME, TAP-UP and ACCEL functions are operated with the same switch. The cruise control main switch is an automatic return type switch which turns on only while operating it in each arrow direction and turns off after releasing it. The dynamic radar cruise control system has two cruise control modes: the constant speed control mode and vehicle-to-vehicle distance control mode.
  1. The vehicle-to-vehicle distance control mode is always selected when starting up the dynamic radar cruise control system.
  2. Operation of the constant speed control mode is the same as that for a conventional cruise control system.

  1. MODE CONTROL
    Pushing the switch to MODE for more than 1 second while driving with the cruise control main switch ON-OFF button on (RADAR READY is on) changes the mode to the constant speed control mode.

  2. SET CONTROL (Constant speed control mode)
    Vehicle speed is stored and constant speed control is maintained when pushing the switch to SET / COAST while driving with the vehicle speed within the set speed range (between the low and high speed limits) after pushing the cruise control main switch ON (RADAR READY is on), and entering the constant speed control mode.

  3. SET CONTROL (Vehicle-to-vehicle distance control mode)
    Vehicle speed is stored and vehicle-to-vehicle control is maintained when pushing the switch to SET / COAST while driving with the cruise control main switch ON (RADAR READY is on), and vehicle speed is within the set speed range (between the low and high speed limits).

  4. COAST CONTROL (Constant speed control mode)
    When the cruise control main switch is set to SET / COAST and held in that position while the cruise control system is operating, the ECM sends a "throttle valve opening angle 0° " demand signal to the cruise control system. Then the vehicle speed, when the cruise control main switch is released, is stored and maintained.

    HINT:
    An actual throttle valve opening angle of 0° is not possible due to the idle speed control, etc.

  5. COAST CONTROL (Vehicle-to-vehicle distance control mode)
    When SET / COAST on the cruise control main switch is pressed and held while the vehicle-to-vehicle distance control mode is in operation, the stored vehicle speed decreases by approximately 5 km/h or 5 mph per second.

  6. TAP-DOWN CONTROL (Constant speed control mode)
    When tapping down the cruise control main switch to SET / COAST (for approximately 0.5 seconds) while the constant speed control mode is in operation, the stored vehicle speed decreases each time by approximately 1.6 km/h (1 mph). When the cruise control main switch is released from SET / COAST and the difference between the driving and stored vehicle speed is more than 5 km/h (3 mph), the vehicle speed is stored and constant speed control is maintained.

  7. TAP-DOWN CONTROL (Vehicle-to-vehicle distance control mode)
    When tapping down the cruise control main switch to SET / COAST (for approximately 0.5 seconds) while the vehicle-to-vehicle distance control mode is in operation, the stored vehicle speed decreases each time by approximately 5 km/h or 5 mph.

  8. ACCELERATION CONTROL (Constant speed control mode)
    The throttle valve motor of the throttle position sensor and motor is instructed by the ECM to open the throttle valve when RESUME / ACCEL on the cruise control main switch is pressed and held while the constant speed control mode is in operation. When the cruise control main switch is released from RESUME / ACCEL, the vehicle speed is stored and constant speed control is maintained.

  9. ACCELERATION CONTROL (Vehicle-to-vehicle distance control mode)
    When RESUME / ACCEL on the cruise control main switch is pressed and held while the vehicle-to-vehicle distance control mode is in operation, the stored vehicle speed increases by approximately 5 km/h or 5 mph per second. Pushing the cruise control main switch to RESUME / ACCEL while following the vehicle in front with the vehicle-to-vehicle distance control mode on does not increase the actual vehicle speed, but changes only the set vehicle speed.

  10. TAP-UP CONTROL (Constant speed control mode)
    When tapping up the cruise control main switch to RESUME / ACCEL (approximately 0.5 seconds) while the constant speed control mode is in operation, the stored vehicle speed increases each time by approximately 1.6 km/h (1 mph). However, when the difference between the driving and the stored vehicle speeds is more than 5 km/h (3 mph), the stored vehicle speed will not be changed.

  11. TAP-UP CONTROL (Vehicle-to-vehicle distance control mode)
    When tapping up the cruise control main switch to RESUME / ACCEL (for approximately 0.5 seconds) while the vehicle-to-vehicle distance control mode is in operation, the stored vehicle speed increases each time by approximately 5 km/h or 5 mph.

  12. MANUAL CANCEL CONTROL
    Performing any of the following cancels the cruise control system while it is in operation (the stored vehicle speed in the ECM is maintained).

    1. Depressing the brake pedal
    2. Moving the shift lever to any position except D (6th, 5th, and 4th gear)
    3. Pushing the cruise control main switch to CANCEL
    4. Turning the cruise control main switch OFF (the stored vehicle speed in the ECM is not maintained).

  13. RESUME CONTROL
    If the cruise control operation was canceled with the stop light switch or the CANCEL switch, and if driving speed is within the set speed range, pushing the cruise control main switch to RESUME / ACCEL restores the vehicle speed memorized at the time of cancellation, and maintains constant speed control. In constant speed mode, once vehicle speed goes below the low speed limit, RESUME operation is not possible even if accelerating up to the low speed limit or more again.


BRAKE CONTROL
The cruise control ECU (distance control ECU) determines the distance to the vehicle in front, relative speed, target decreasing speed and deceleration rate. Based on this data, the ECU may transmit a brake demand signal to the skid control ECU via the ECM.

DOWNSHIFT CONTROL
While the cruise control system is in operation, the gear may downshift from overdrive (6th) to 5th on an uphill road. After the gear is shifted down to 5th, if the system determines that the uphill inclination has become smaller based on the throttle valve opening angle, the gear automatically returns to overdrive (6th).

AUTO CANCEL (FAIL-SAFE)
This system has an automatic cancellation function (fail-safe) (Click here).