GB/T 20608-2006Intelligent transportation systems -- Adaptive cruise control systems -- Performance requirements and test procedures (English PDF)

4.1 Symbols

The following symbols apply to this document.

alateral_max. maximum designed lateral acceleration on a curve, expressed in (m/s²).

astopping. longitudinal acceleration of the target vehicle during automatic parking capability test, expressed in (m/s²).

CTT. parameter of infrared reflectivity of the test target, expressed in (m²/sr).

c. clearance, expressed in (m).

cmin. minimum clearance at all vehicle speeds in a steady state (including the hold state), expressed in (m).

d0.critical interval for determining whether it is necessary to detect the target vehicle, expressed in (m).

d1.critical distance for determining whether it is necessary to measure distance or relative speed, expressed in (m).

d2.distance required for measurement, expressed in (m).

dmax. maximum detection range on a straight road, expressed in (m).

R. curve radius, expressed in (m).

Rmin. minimum curve radius, expressed in (m).

RCS. scattering cross-sectional area of radar signals, expressed in (m²).

v. instantaneous vehicle speed, expressed in (m/s).

vcircle. maximum vehicle speed on a curve with an acceleration of alateral_max, expressed in (m/s).

vcircle_start. initial vehicle speed when entering a curve of radius R, expressed in (m/s).

vlow. minimum vehicle speed required for automatic acceleration and deceleration, expressed in (m/s).

vset_max. maximum selectable set speed, expressed in (m/s).

vset_min. minimum selectable set speed, expressed in (m/s).

vstopping. speed of target vehicle during automatic parking capability test, expressed in (m/s).

vvehicle_end. vehicle speed at the end of the test, expressed in (m/s).

vvehicle_max. maximum vehicle speed during the test, expressed in (m/s).

vvehicle_start. vehicle speed at the start of the test, expressed in (m/s).

tau. time gap, expressed in (s).

taumax(v). at vehicle speed v, maximum time gap obtained, expressed in (s).

taumax. maximum time gap, expressed in (s).

taumin. minimum time gap, expressed in (s).

4.2 Abbreviations

The following abbreviations apply to this document.

ABS. Anti-lock Braking System

ACC. Adaptive Cruise Control

FSRA. Full Speed Range Adaptive Cruise Control

LSRA. Limited Speed Range Adaptive Cruise Control

5.1 Operating Principle

The main function of the ACC system is to perform longitudinal control of the vehicle based on the driver’s operating commands, the subject vehicle’s motion state, and the distance information between the subject vehicle and forward vehicle, thereby adapting to the motion of the forward vehicle, and simultaneously provide feedback of the system state to the driver. The onboard equipment can provide the driver with speed-setting suggestions. The operating principle is shown in Figure 2.

Figure 2 -- Operating Principle of Adaptive Cruise Control System

5.2 System Types

The ACC system is classified into FSRA and LSRA systems based on the applicable operating speed range, as shown in Table 1.The vehicle user’s instruction manual shall describe the deceleration capability of the ACC system, and all ACC types shall include active brake control.

Table 1 -- ACC System Types

6.1 ACC System States

6.1.1 The ACC system has three states. ACC off, ACC standby, and ACC active. The ACC system states and their transitions are shown in Figure 3.

Figure 3 -- ACC System States and Transitions

6.1.2 If the ACC system is off, it shall stop working.

6.1.3 If the ACC system is in standby state, it shall be able to be triggered and enter ACC active state or be turned off and enter off state.

6.1.4 If the ACC system is active, it shall be able to adjust the subject vehicle’s speed and/or time gap.

6.2 State Transitions

6.2.1 6.2.2 ~ 6.2.6 are the minimum requirements for the ACC system and constitute its basic system behavior.

6.2.2 When the ACC is active, the subject vehicle shall maintain a certain time gap with the target vehicle or a preset speed (whichever is lower) through automatic speed control. The transition between these two control modes is automatically completed by the ACC system.

6.2.3 Under stable driving conditions, the time gap shall be automatically adjusted by the ACC system or by the driver.

6.2.4 If there are multiple forward vehicles, the ACC system shall be able to identify and follow the closest target vehicle in the lane.

6.2.5 The following applies only to FSRA type systems.

a) When the system is in “hold” state, it shall be able to automatically brake to bring the subject vehicle to a standstill;

b) After the subject vehicle stops, the ACC system shall switch from follow-up control state to FSRA hold state within 3 seconds;

c) The switch from FSRA hold state to ACC follow-up control mode or ACC speed control mode shall be triggered by driver’s command or automatically by the system.

6.2.6 The following applies only to LSRA type systems.

a) If the speed of the subject vehicle is below vlow, the ACC system shall not enter ACC active state from ACC standby state;

b) If the system is in ACC active state and the vehicle speed drops below vlow, the ACC system shall not automatically accelerate the vehicle.

7.1 Basic Requirements

7.1.1 The ACC system shall provide the driver with a method to select and set the desired vehicle speed, or provide suggestions to the driver through onboard equipment (e.g., traffic sign recognition systems).

7.1.2 If the ACC system is in follow-up or speed control state, and the driver applies a braking force greater than the ACC system’s braking force, or if there is braking action, the system shall switch to ACC standby state. For FSRA type systems, if the system is in FSRA hold state, when the driver applies the brakes, switching to ACC standby state is not mandatory, as shown in

Figure 3.

7.1.3 If the ACC system is performing active brake control and the driver simultaneously applies a braking force, the ACC system shall not reduce its instantaneous braking response.

7.1.4 If both the driver and the ACC system request engine or electric motor power control, the greater of the two requests shall prevail, but the driver’s control of the vehicle shall always be guaranteed. If the driver’s braking demand is higher than that of the ACC system, the ACC system shall relinquish braking control and immediately apply a braking force. The ACC system shall not have a response delay to the driver’s acceleration control commands.

7.1.5 The wheel locking time after the activation of active brake shall not exceed the time allowed by ABS. The ACC system shall not interfere with the ABS system.

7.1.6 The wheel slip time caused by the engine or electric motor power control action of the

ACC system shall not exceed the allowable value of the traction control system. The ACC system shall not interfere with the traction control system.

7.1.7 The ACC system shall automatically adjust the time gap to adapt to the driving environment (for example, severe weather), but the adjusted time gap shall be greater than the minimum time gap set by the driver.

7.1.8 If the ACC system allows the driver to set the time gap, the value shall be initialized using the following methods.

a) If the ACC system stores the last set time gap after being turned off, then, when the system is re-activated, the value shall be clearly displayed;

b) If the ACC system does not store the last set time gap after being turned off, then, the default value shall be used (this value shall be greater than or equal to 1.5 s).

7.1.9 If the vehicle is equipped with both an ACC system and a conventional cruise control system, they shall not automatically switch.

7.2 Display

7.2.1 The ACC system shall at least provide the driver with information such as the ACC system state, set speed, and time gap, etc. The displayed information shall not affect driving behavior.

7.2.2 If the ACC system is turned off or malfunctions, the driver shall be promptly alerted, and the alert symbol shall comply with the provisions of GB/T 44298.

7.2.3 If the vehicle is equipped with both an ACC system and other driver assistance systems, the driver shall be alerted of the currently active system.

7.2.4 If a forward vehicle is detected, the “Vehicle Detected” signal in the ACC system shall be activated and displayed.

7.3 Symbols of the ACC System

If symbols are used to identify the functions and fault states of the ACC system, they shall comply with the provisions of GB/T 44298.

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