FUNCTION OF MAIN COMPONENTS
The main components in the dynamic radar cruise control system have the following functions:
| Component | Function | |
|---|---|---|
| Millimeter Wave Radar Sensor Assembly |
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| Driving Support ECU Assembly |
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| Cruise Control Switch | ON-OFF Button | Turns the cruise control system on and off. |
| MODE Switch | Switches between 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 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 due to operation of 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 3 levels: long, middle, and short. | |
| Hybrid Vehicle Control ECU |
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| MG ECU | Built into the inverter with converter assembly. Controls the motive force of MG2 in accordance with signals from the hybrid vehicle control ECU. | |
| ECM | Actuates the throttle control motor in accordance with the signals from the hybrid vehicle control ECU. | |
| Brake Booster with Master Cylinder Assembly | Skid Control ECU |
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| Brake Actuator | Actuates the brakes in accordance with the signals from the skid control ECU. | |
| Windshield Wiper Motor | Transmits windshield wiper switch information (HI position) to the driving support ECU assembly. | |
| Combination Meter Sub-assembly | Cruise Control Indicator Light (Constant Speed Control Mode) |
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| Cruise Control Indicator Light (Vehicle-to-vehicle Distance Control Mode) |
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| Cruise Control SET Indicator Light | Illuminates when the vehicle speed is set. | |
| Buzzer | If 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 system operating conditions. | |
| MG2 | Generates motive force for the wheels. | |
| Throttle Body Assembly | Throttle Control Motor | Adjusts the throttle valve opening angle in accordance with signals from the ECM. |
| Throttle Position Sensor | Detects the throttle valve opening angle and outputs it to the ECM. | |
| Stop Light Control ECU Assembly | Illuminates the stop lights in accordance with an light illumination request signal from the skid control ECU. | |
| Skid Control Buzzer Assembly | Sounds receiving a signal from the millimeter wave radar sensor assembly and alerts the driver that the distance between 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 hybrid vehicle control ECU. | |
| Shift Lock Control Unit Assembly | Shift Lever Position Sensor (Shift Sensor) | Detect the shift lever position and transmit signals to the hybrid vehicle control ECU. |
| Shift Lever Position Sensor (Select Sensor) | ||
| Spiral Cable with Sensor Sub-assembly | Steering Angle Sensor | Detects the angle and direction of steering and transmits signals to the driving support ECU assembly. |
| Airbag ECU Assembly | Yawrate Sensor | Detects the yawrate of the vehicle and transmits signals to the driving support ECU assembly. |
| Stop Light Switch Assembly | Detects the brake pedal being depressed and transmits its signal to the driving support ECU assembly. | |
SYSTEM CONTROL
The dynamic radar cruise control system is controlled by the driving support ECU assembly. The driving support ECU assembly increases and decreases the vehicle speed by controlling the engine, MG2 and brake through the motive force request signals.
The combination meter sub-assembly informs the driver of the control conditions.
The cruise control switch (mode switch) is used for switching between constant speed control mode and vehicle-to-vehicle distance control mode. The mode in which the cruise control system starts is the vehicle-to-vehicle distance control mode.
For vehicles with the dynamic radar cruise control system, constant speed control mode is controlled by the driving support ECU assembly, which outputs signals to the MG ECU.
Vehicle-to-vehicle distance control mode is controlled by the millimeter wave radar sensor assembly and driving support ECU assembly. Thus, the signals are output to the actuators and the ECU while exchanging data as indicated below.
FUNCTION
Function List
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 | Controls the motive force through the hybrid vehicle control ECU and skid control ECU, and adjusts the vehicle speed to the set vehicle speed. | X | X |
| Deceleration Control | Performs engine, MG2 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. | - | X |
| 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. The actual distance maintained for each distance level (long, medium and short) varies in accordance with vehicle speed. | - | X |
| 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. | - | X |
| Set Control |
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X | - |
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- | X | |
| Low Speed Limit Control | The low speed limit is the lowest speed that cruise control can be operated at and it is designed to be approximately 40 km/h (25 mph). The cruise control cannot be operated below that speed. If the vehicle speed drops below that speed while the cruise control is set and working to maintain vehicle speed, the cruise control will be canceled automatically. The set vehicle speed is kept in memory. | X | X |
| COAST Switch Control | When the cruise control switch is held to the -SET side, the vehicle speed and the set vehicle speed change as follows, according to the mode: | X | X |
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X | - | |
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- | X | |
| 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: | X | X |
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X | - | |
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- | X | |
| ACC Switch Control | When the cruise control switch is held to the +RES side, the vehicle speed and the set vehicle speed change as follows, according to the mode: | X | X |
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X | - | |
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- | X | |
| 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: | X | X |
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X | - | |
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- | X | |
| 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 moved to the +RES side) to reach the vehicle speed that was set at the time the driver canceled cruise control. | X | X |
| If the vehicle ahead changes driving lanes during follow-up control, the vehicle speed is gradually increased to the set vehicle speed. At this time, the vehicle speed can be increased promptly by moving the cruise control switch to the +RES side. | - | X | |
| Manual Cancel Control |
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X | X |
| Automatic Cancel Control | When an automatic cancel signal is sent to the driving support ECU assembly, cruise control speed control operation is canceled. At this time, the type of warning sent to the driver and the control resumption condition vary according to the cancel signal. | X | X |
| Mode Switching Control |
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X | X |
| Other Cancelation Condition |
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X | X |
X: Available
-: Not Available
*1: Models for Europe
*2: Except model for Europe
Constant Speed Control
The driving support ECU assembly compares the actual vehicle speed (wheel speed signal from the skid control ECU) with the set vehicle speed under constant speed control in each control mode. When the actual vehicle speed differs from the set vehicle speed, the driving support ECU assembly calculates the motive force required to achieve the set vehicle speed and transmits motive force request signals to the hybrid vehicle control ECU, thus controlling the motive force optimally and adjusting the actual vehicle speed to the set vehicle speed.
In vehicle-to-vehicle distance control mode, the driving support ECU assembly performs deceleration control or follow-up control or acceleration control based on the information about the vehicle ahead transmitted from the millimeter wave radar sensor assembly.
Deceleration Control
The driving support ECU assembly calculates the target deceleration rate in accordance with signals from the millimeter wave radar sensor assembly, and transmits a motive force request signal to the hybrid vehicle control ECU and the skid control ECU. Upon receiving this signal, these ECUs control the motive force and decelerate the vehicle.
This control is not performed in the presence of a parked vehicle or object, or below the settable vehicle speed range.
If the driving support ECU assembly determines that further deceleration is necessary, it transmits a brake request signal to the skid control ECU. Upon receiving this signal, the skid control ECU then activates the brake actuator to apply the brakes.
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 ECU assembly, in order to inform anyone who might be following the vehicle.
If the vehicle is not decelerating adequately, the millimeter wave radar sensor assembly sounds the skid control buzzer assembly based on a request signal from the driving support ECU assembly. The buzzer is sounded to urge the driver to depress the brake pedal.
Follow-up Control
After performing deceleration control, the driving support ECU assembly transmits motive force request signals to the hybrid vehicle control ECU and the skid control ECU so that the vehicle can follow the vehicle ahead while maintaining the proper vehicle-to-vehicle distance. The actual distance maintained for each distance level (long, middle and short) varies in accordance with vehicle speed. Upon receiving these signals, these ECUs control the motive force in order to perform follow-up control.
3 levels (long, middle, and short) of vehicle-to-vehicle distance can be selected by operating the distance control switch.
Acceleration Control
If the driving support ECU assembly detects that either the vehicle ahead or the driver has changed lanes, a motive force request signal is transmitted to the hybrid vehicle control ECU in order to attain the set vehicle speed. Upon receiving this signal, the hybrid vehicle control ECU controls the motive force of the engine and MG2 in order to perform acceleration control.
Automatic Cancel Control
If any of the conditions listed below occur while the vehicle is being driven using cruise control, speed control by the cruise control system will be canceled. Then, the following warning items will appear for the driver.
| Situation | Warning | |||||
|---|---|---|---|---|---|---|
| Multi-information Display | |
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Buzzer in the combination meter assembly | |
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CHECK CRUISE CONTROL SYSTEM | Illuminates | Does not illuminate | Does not illuminate | Does not illuminate | - |
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CHECK CRUISE CONTROL SYSTEM | Illuminates | Does not illuminate | Does not illuminate | Does not illuminate | Sounds Once |
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- | Does not illuminate | Does not illuminate | Does not illuminate | Does not illuminate | - |
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- | Does not illuminate | Illuminates | Does not illuminate | Does not illuminate | - |
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- | Does not illuminate | Illuminates | Does not illuminate | Does not illuminate | - |
| Situation | Warning | |||||
|---|---|---|---|---|---|---|
| Multi-information Display | |
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Buzzer in the combination meter assembly | |
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CHECK CRUISE CONTROL SYSTEM | Illuminates | Does not illuminate | Does not illuminate | Does not illuminate | Sounds Once |
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CHECK CRUISE CONTROL SYSTEM | Illuminates | Does not illuminate | Does not illuminate | Does not illuminate | Sounds Once |
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- | Does not illuminate | Does not illuminate | Does not illuminate | Does not illuminate | - |
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CLEAN RADAR SENSOR | Illuminates | Does not illuminate | Does not illuminate | Does not illuminate | Sounds Once |
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CRUISE CONTROL NOT AVAILABLE | Illuminates | Does not illuminate | Does not illuminate | Does not illuminate | Sounds Once |
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- | Does not illuminate | Does not illuminate | Illuminates | Does not illuminate | Sounds Twice |
CONSTRUCTION
Cruise Control Switch
The cruise control switch consists of the ON-OFF button and the +RES, MODE, -SET and CANCEL switches. The +RES, MODE, -SET and CANCEL switches are operated by moving the lever in the 4 directions indicated.
The switches in the cruise control switch are of the automatic reset (normally open) type that turn on only when the switch is being operated and turn off as soon as the driver releases the switch. Furthermore, the functions of the switches are active only when the cruise control system has been turned on using the ON-OFF button on the cruise control switch.
| *1 | Cruise Control Switch | - | - |
| *a | ON-OFF Button | *b | +RES Switch |
| *c | MODE Switch | *d | -SET Switch |
| *e | CANCEL Switch | - | - |
Distance Control Switch
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.
| *1 | Distance Control Switch | - | - |
If the power switch is turned off and back to on (IG), the system will default to "long".
The vehicle-to-vehicle distance is as follows:
| Mode | Vehicle-to-vehicle Distance* |
|---|---|
| Long | Approximately 50 m (160 ft.) |
| Middle | Approximately 40 m (130 ft.) |
| Short | Approximately 30 m (100 ft.) |
Tech Tips
*: While driving at a speed of 80 km/h (50 mph).
Millimeter Wave Radar Sensor Assembly
The millimeter wave radar sensor assembly consists of a millimeter wave radar circuit, signal processing circuit, and CPU.
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.
The reception antennas receive the millimeter wave radar waves that have been reflected.
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.
| *1 | Millimeter Wave Radar Sensor Assembly | - | - |
| *a | Detection Distance: Approximately 150 m | *b | Horizontal Angle: About 20° |
| *c | Vertical Angle: About 8° | - | - |
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 reflected waves are received by the millimeter wave radar circuit. The detection distance is approximately 150 m (490 ft.). |
| Azimuth | Calculated from the reception angle of the millimeter wave radar reflections received. The detection angle has a horizontal range of approximately 20° and a vertical range of approximately 8°. |
| Relative Speed | Calculated by utilizing the change (Doppler effect*) that occurs in the frequency 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 a higher frequency as it approaches, and to be a lower frequency as it recedes. This phenomenon is created because when an object is located far away, the radio waves are perceived at higher frequency than those of the radio source.
Tech Tips
Millimeter wave radar uses an extremely high frequency band between 30 GHz and 300 GHz, with an extremely short wavelength between 1 and 10 mm (0.04 to 0.40 in.) in a vacuum. The millimeter wave radar sensor of the pre-crash safety system uses frequencies in the 76.5 GHz band.
The millimeter wave radar is less affected by weather conditions such as rain, fog, or snow, and provides excellent characteristics for recognizing objects. Therefore, it is well suited to the pre-crash safety system and the dynamic radar cruise control system.
An SST is used if radar axis adjustment is needed. For details, refer to the Repair Manual.
OPERATION
Combination Meter Sub-assembly
The combination meter sub-assembly has a cruise control indicator light (constant speed control mode), cruise control indicator light (vehicle-to-vehicle distance control mode), cruise control SET indicator light, buzzer and display to provide warnings and regarding the dynamic radar cruise control system.
The multi-information display displays the set vehicle speed, vehicle ahead mark, and warning message.
Examples are shown below for the illumination or display of each indicator light or the multi-information display.
| Condition | Multi-information Display | |
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Buzzer |
|---|---|---|---|---|---|
| Being Controlled* | |
Does not illuminate | Illuminates | Illuminates | - |
| System Check | CHECK CRUISE CONTROL SYSTEM | Illuminates | Does not illuminate | Does not illuminate | Buzzer in the combination meter assembly sounds once |
Tech Tips
*: While driving at a set speed of 100 km/h (62 mph).
| Condition | Display | |
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Buzzer |
|---|---|---|---|---|---|
| Set Standby | RADAR READY | Does not illuminate | Illuminates | Does not illuminate | - |
| Under Constant Speed Control (No Vehicle Ahead, Short)* | |
Does not illuminate | Illuminates | Illuminates | - |
| Under Follow-up Control (Vehicle Ahead, Middle)* | |
Does not illuminate | Illuminates | Illuminates | - |
| Deceleration Control/Vehicle Approach Warning (Vehicle Ahead, Long)* | |
Does not illuminate | Illuminates | Illuminates | Skid Control Buzzer Sounds Continuously |
| Millimeter Wave Radar Sensor Assembly is Dirty | CLEAN RADAR SENSOR | Illuminates | Does not illuminate | Does not illuminate | Buzzer in the combination meter assembly sounds once |
| Poor Weather Conditions | CRUISE CONTROL NOT AVAILABLE | Illuminates | Does not illuminate | Does not illuminate | Buzzer in the combination meter assembly sounds once |
| System Check | CHECK CRUISE CONTROL SYSTEM | Illuminates | Does not illuminate | Does not illuminate | Buzzer in the combination meter assembly sounds once |
| Beam Axis Adjustment | ADJUSTING FRONT RADAR BEAM | Does not illuminate | Does not illuminate | Does not illuminate | Skid Control Buzzer Sounds Once |
Tech Tips
*: While driving at a set speed of 100 km/h (62 mph).
DIAGNOSIS
If a malfunction occurs in the dynamic radar cruise control system during cruise control operation, the driving support ECU automatically cancels speed control by the cruise control system, 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 driving supporte ECU memorizes the malfunction in the form of 5-digit Diagnostic Trouble Codes (DTCs).
The 5-digit DTC can be read by connecting the Global TechStream (GTS) to the DLC3. For details, refer to the Repair Manual.