Part 1
Speed Control
NOTE:
A = Hardwired; D = High speed CAN (controller area network) bus; O = LIN (local interconnect network) bus
SPEED CONTROL
The speed control system is integrated with the engine management system and uses fueling intervention to automatically maintain a set vehicle speed. Once engaged, the system can also be used to accelerate the vehicle without using the accelerator pedal. The speed control system comprises the following components:
- '+' and '-' (set/accelerate and decelerate) steering wheel switches
- Resume switch
- Cancel switch
- Clock spring
- Speed control warning indicator.
The speed control system also uses inputs from the brake pedal switch, the APP (accelerator pedal position) sensor, the ECM (engine control module) and the ABS (anti-lock brake system) module.
The speed control is operated by the driver using only the steering wheel switches. When speed control is active, the ECM (engine control module) regulates the PWM (pulse width modulation) signals to the fuel injectors to adjust the fuel supply as required to maintain the set speed.
During speed control operation, the ECM (engine control module) controls vehicle speed by adjusting fuel injection duration and timing. When the accelerator pedal is pressed with speed control active, the ECM (engine control module) outputs a calculated throttle angle signal in place of the actual throttle angle signals produced by the APP (accelerator pedal position) sensor. The calculated throttle angle is derived from fuel demand based on the torque required to overcome the rolling resistance (vehicle motion drag).
The minimum set speed for speed control is 20 mph (32 (km/h). Speed control is automatically suspended if the following conditions apply:
- Vehicle speed falls below 20 mph (32 km/h).
- The brake pedal is pressed.
- The cancel button is pressed.
- Neutral, park or reverse gear is selected.
- The difference between actual speed and the set speed is too great.
- If the accelerator pedal is used to accelerate beyond the set speed for too long (More than 5 minutes).
- Stability control system intervention
- System error causes shut-off.
There are 4 standard speed control switches:
- Set speed + accelerate switch
- Decelerate - switch
- Cancel switch
- Resume switch.
The standard speed control switches are located on the RH (right-hand) side of the steering wheel. The switches are resistive ladder type switches which vary the resistance of a voltage signal sent to them. The resistive ladder is wired to a control module within the switch assembly, the control module is a LIN (local interconnect network) node which transmits the data to the CJB (central junction box) which passes the data onto the high speed CAN (controller area network) bus. In the event of the ECM (engine control module) logging a cruise switch fault DTC (diagnostic trouble code), fault finding should start at the switch assembly and clockspring. The ECM (engine control module) diagnostic detects that the switch
assembly control module hasn't provided an updated live counter.
Engage Speed Control
Speed control is engaged by pressing the set speed accelerate + switch. Once engaged the speed can be increased by one of 3 methods:
- Press and hold the set speed accelerate + switch which will cause the vehicle to accelerate. When the switch is released the attained speed will be set as the cruise speed.
- Repeatedly pressing the set speed accelerate + switch. Each press increases the vehicle speed by 1 mph (2 km/h).
- Use the accelerator pedal to increase the vehicle speed. Once the required speed is reached, a single press of the set speed accelerate + switch will set the cruise speed.
When the target speed has been set, a green marker will appear on the outer circumference of the speedometer in the instrument cluster, adjacent to the set speed. If the set speed is changed the marker will move accordingly. If the speed control is cancelled the marker changes to a gray color until the resume switch is pressed to re-engage speed control, when it changes back to a green color.
Reduce Cruising Speed
The set speed can be reduced by pressing and holding the decelerate - switch until the required speed is reached. When the switch is released the speed is reset at that value. The set speed can be reduced incrementally by pressing and releasing the decelerate - switch. Each press will reduce the speed by 1 mph (2 km/h). Adaptive speed control braking can be induced by using the - switch to decelerate the vehicle
Set Speed Adjustment
Speed control adjustment is limited around the current vehicle speed. This means speed adjustment won't occur when resuming or if the vehicle speed is noticeably different to set speed. This is noticeable when resuming speed control and a large difference exists between the set speed and the current speed. The driver can set a new speed, but can't adjust the old speed.
Suspend Speed control
Suspending speed control means speed control has been deactivated without loss of the memory speed. In all suspend events the memory speed is maintained. Speed control can be suspended in a number of ways, as described in the general description.
A single press of the RESUME switch will resume speed control at the previously set speed.
NOTE:
In the event that a memory speed has been lost during a driving cycle, confirm with the customer if the "Cruise Not Available" message was observed. Loss of memory speed implies a fault has occurred. Cruise not available may only be displayed on demand for some errors, so cruise needs to be requested via set + to drive the message.
ADAPTIVE SPEED CONTROL
The adaptive speed control system utilizes the following components:
- Adaptive speed control radar sensor
- Steering wheel gap increase and decrease control switches
- ECM (engine control module)
- Throttle intake manifold - Electric throttle
- ABS (anti-lock brake system) module and pump
- Adaptive speed control warning indicator (in the instrument cluster)
- Forward alert warning indicator.
The adaptive speed control system uses a forward looking radar sensor to scan the road ahead, looking for objects that are moving at a different rate to itself. When a target is identified the adaptive speed control system will monitor the time gap between it and the target vehicle. When that gap falls below a set driver selected level the adaptive speed control system will intervene slowing the vehicle by backing off the throttle and/or applying the brakes, until the correct gap is attained. The driver can chose between four gap settings, 1, 1.4, 1.8 and 2.2 seconds.
The system will detect but not react to the following:
- Vehicles in the oncoming lane
- Stationary vehicles
- Pedestrians
- Vehicles not in the same lane
- Motorcycles.
Adaptive speed control is active when the vehicle is moving. Adaptive speed control only functions when a set speed is entered via the SET + switch. The adaptive speed control system only intervenes with the set speed when it detects a target vehicle, and then only if the minimum time gap is breached.
It is important to note that the system is intended for use in limited driving situations, does not remove control and responsibility from the driver, and at all times can be quickly overridden. The adaptive speed control system is not a collision warning system and will not react to stationary objects. The system does not operate below a minimum speed of approximately 20 mph (32 km/h) since it is unsuitable for use in cities or congested traffic. The system is best suited to main roads/ highways with gradual bends.
The ECM (engine control module), electric throttle and throttle control are unchanged from those used for non adaptive speed control variants.
Radar Sensing
The adaptive speed control system is based on the use of a front mounted radar sensor. The sensor transmits a 1.5° wide beam forward of the vehicle and detects the returning signals reflected off other vehicles and objects ahead.
The 1.5° wide radar beam is electronically scanned at a rate of 10 sweeps/second across a total arc of 15° centered on the longitudinal axis of the vehicle. The radar operates at millimetric wavelengths (76 - 77 GHz) and transmits a frequency modulated continuous wave signal at a relatively low power level (no high power pulses).
With the ignition switched ON, no radar transmissions are emitted until the vehicle is in motion.
The radar sensor detects three primary parameters of objects within the scanned arc. These are:
- Range
- Relative velocity
- Angle.
Range
The radar sensor detects the presence and ranges of different vehicles and objects within the scanned arc up to a distance of approximately 130 meters (426.5 feet). The transmitted signal frequency changes continuously in a cyclic pattern (modulation). This means that, in the time taken for the signal wave front, to travel to and from a target vehicle (or other object), the transmission frequency will have changed. The difference between the received signal frequency and the new transmission frequency is proportional to the distance between the transmitting vehicle and the target vehicle.
Relative Velocity
When the signal is reflected off a vehicle moving at a different speed (opening or closing the gap) an effect known as the 'Doppler Shift' causes an extra frequency modulation to be imposed on the signal. This doppler frequency varies with the relative speed of the vehicle being followed, enabling the system to differentiate between vehicles traveling at different speeds and also between moving vehicles and stationary objects.
Angle
Using a narrow angle beam to scan horizontally enables the system to distinguish between vehicles in different lanes and between vehicles and roadside objects.
Follow Mode
In follow mode a set speed is selected in the normal speed control manner and this speed is maintained until a slower vehicle is encountered in the lane ahead. When the vehicle ahead comes within the effective range of the radar sensor, the system identifies it as a target vehicle and an icon is illuminated on the instrument cluster to indicate that the system is in "follow mode". When the distance between the two vehicles closes to a set time gap, the adaptive speed control system closes the throttle and if necessary applies the brakes to maintain the set time gap. Follow mode is effectively a closed loop system. If several vehicles are ahead, the closest vehicle is chosen as the target to follow. If the target vehicle moves out of radar range, or if either vehicle changes lane or drops below the minimum operating speed, the system exits follow mode and the follow mode icon is extinguished. The adaptive speed control system will only raise its speed to the originally set
speed, it will not accelerate past this speed to maintain a time gap.
Driver operation of the foot brake or control switches will immediately cancel adaptive speed control. A 'cruise cancelled' message will be displayed to the driver in the message center.
When the vehicle is in follow mode, the follow mode warning indicator is illuminated in the instrument cluster. The gap setting will be displayed at the time of the set event, NOT on the detection of every target, this is to prevent overwriting the instrument cluster tachometer everytime a target is detected.
Follow Mode Warning Indicator
Forward Alert
Limited detection and warning of vehicles ahead is provided during adaptive cruise control operation by the forward alert warning. The enhanced forward alert warning provides additional warnings when the adaptive cruise control is not engaged. If a vehicle is detected close ahead, a warning tone will be emitted and a 'Forward Alert' message will be displayed. Throttle and braking intervention is NOT applied
The forward alert system is active when the warning indicator in the instrument cluster is illuminated. Forward alert does not initiate any action, the driver must take the appropriate action when the message is displayed. The system monitors driver intervention and may not issue the warning if the driver has taken the appropriate action (braking, steering or indicating) early enough.
Forward Alert Warning Indicator
The forward alert system uses the adaptive speed control system components. Forward alert is turned on and off independently of adaptive speed control, via the instrument cluster menu. Forward alert will notify the driver by means of a chime, and warning indicator in the instrument cluster and indication in the message center, when a target vehicle comes into range. The system will NOT use throttle or brake intervention to slow the vehicle.
When forward alert is selected on or off, the instrument cluster sends the forward alert information to the radar sensor on the CAN (controller area network) bus. When a forward alert sensitivity adjustment is made using the time gap increase/decrease switches on the RH (right-hand) side of the steering wheel. The switches are connected via fly leads to the clockspring and pass a signal a LIN (local interconnect network) bus signal, via the clockspring to the CJB (central junction box). The CJB (central junction box) routes the selected sensitivity adjustment signals to the adaptive speed control radar sensor on the high speed CAN (controller area network) bus.
NOTE:
This system is intended as a driver aid and should be used as such. The system is NOT a collision warning or avoidance device.
The system sensitivity can be adjusted in the same manner as the Adaptive Speed Control, via the steering wheel mounted switches. Each adjustment is accompanied by a message in the message center.