Lane Keep Assist Steering Intervention

Some of the latest active safety features available on GM models employ sophisticated camera-, radar- and sensor-based technologies to help assist drivers avoid a collision or reduce its impact.


Lane Keep Assist (RPO UHX) — available on many newer GM models — uses a number of advanced components to help drivers avoid crashes due to unintentionally drifting from their lane. The components include:

• Front View Camera Module
• Lane Keep Assist Switch/Control Indicator (Fig. 1)
• Instrument Cluster/Vehicle Direction Display
• Radio (for warning beeps/chimes)
• Safety Alert Seat (if equipped)
• Yaw Rate Sensor
• Electric Power Steering



Fig. 1


How It Works


For Lane Keep Assist to begin providing assistance, the following must occur:

• Vehicle speed is between 37 mph (60 km/h) and 111 mph (180 km/h)
• Lane markings are clearly visible
• The system is turned on using the On/Off button
• Lane marker width and radius meet pre-set criteria (not too wide or narrow and the curve of the road is not too tight)


The camera detects the lane markings on the road. The front view camera module communicates via serial data with the instrument cluster, radio, and memory seat module to request visual indicators and, in rare instances, audible or haptic alerts. The Lane Keep Assist indicator on the instrument cluster is green when a lane marking is detected and other operating conditions have been met, indicating that the system is in the “ready to assist” mode.


TIP: If the system cannot detect lane markings, it may be due to snow, rain, or other driving conditions, or the windshield area in front of the camera or the camera lens may be blocked by fog, dirt, damage to the windshield or other elements. The vehicle should be kept clean for proper operation.


Stage 1 — Lane Keep Assist Intervention


The system has two driver interventions. When it is determined that the vehicle has unintentionally approached a detected lane marking without a turn signal being activated in that direction, and the driver has not actively responded by either steering, accelerating, or braking, the electric power steering system will provide a gentle, momentary correction (torque input to the steering) to help guide the vehicle back on course. Lane Keep Assist does not continuously steer the vehicle. This steering pushback is the first stage of warning/intervention.


TIP: The Lane Keep Assist indicator will turn amber when torque is applied to the steering. There are no chimes or haptic seat warnings at this point of Lane Keep Assist operation.


The steering intervention is based on the forward looking sensor outputs, such as lateral offset of the vehicle, relative yaw angle and time to line crossing. In addition, other vehicle dynamics signals are needed, e.g. velocity, steering angle, yaw rate, for the purpose of a driver suppression of the steering intervention. The electric power steering uses a torque sensor to detect driver inputs and relays that information to the front view camera module.


Stage 2 — Lane Departure Warning


If active driver steering is not detected, the second stage warning/intervention is a Lane Departure Warning (RPO UFL) that may activate as the vehicle is crossing the lane marking, alerting the driver through several beeps or a Safety Alert Seat vibration, if equipped. The seat vibration will take place on the side of the seat where the lane departure occurs. In addition, the amber Lane Keep Assist indicator will flash.


The Safety Alert Seat must be turned on in the vehicle settings in order for haptic seat feedback to occur.


TIP: Most commonly, the driver applies more torque to the steering wheel to overcome the Lane Keep Assist intervention. As a result, Lane Departure Warning alerts are rare because they only occur if the driver does not put significant torque onto the steering wheel and the Lane Keep Assist steering intervention was not enough to prevent a lane departure. This circumstance tends to happen only at the entrance to some curves.



Testing the System


Lane Keep Assist intervention may not occur when expected by some drivers while approaching a lane marking. Lane Keep Assist replaced Lane Departure Warning for 2016 (although Lane Departure Warning remains a key component) and operation is slightly different.


For example, if the driver tries to “test” the Lane Departure Warning alert and overcomes the steering correction so that the vehicle intentionally crosses the lane marker, the Lane Departure Warning system may interpret this as active steering and, in many cases, may not provide an alert. Consequently, alerts will occur less frequently as the Lane Keep Assist system provides steering input than with the previously used Lane Departure Warning system.


TIP: If a customer expresses concern that a Safety Alert Seat vibration or warning chime did not occur, verify that there are not any issues with the vehicle’s operation or DTCs set and then explain the proper operation of the Lane Keep Assist and Lane Departure Warning systems.


External Influences


Proper functionality of the Lane Keep Assist system may be affected by outside factors, including:

• Nearby vehicles ahead (tailgating)
• Sudden lighting changes, such as going through a tunnel
• Banked roads
• Poor lane markings


Should these conditions exist, the driver is advised to turn off the system. This does not indicate a system failure. Also, drivers should not use Lane Keep Assist while towing a trailer or traveling on slippery roads.


Here’s a video demonstration of how the system works. (Fig. 2)



Fig. 2

– Thanks to Charles Green and Ray Kiefer



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