GB/T 43947-2024General technical requirements for chassis-by-wire of low speed automated vehicle (English PDF)

3 Terms and definitions

3.1 autonomous-service-vehicle: a special-purpose working vehicle fitted with a driving automation system and dedicated automatic control equipment, having no driving cab, used in specific scenarios such as delivery, transport, retail, patrolling and sweeping.

3.2 chassis-by-wire: a chassis with a certain load-carrying capacity, made up of a drive-by-wire system, a brake-by-wire system, a steer-by-wire system and other systems, controlled in the form of electrical signals and driven through a control device or a driving automation system. A note states that control devices include manual control devices and remote driving systems, the manual control device being a remote controller with locking and unlocking functions.

3.3 to 3.5 drive-by-wire system, brake-by-wire system and steer-by-wire system: systems that use by-wire techniques such as electronic circuits and communication transmission to receive commands from the driving automation system or the control device and to control, respectively, the driving, the braking and the steering of the low-speed chassis-by-wire.

3.6 response time: the difference between the moment at which the driving automation system or the control device issues a command and the moment at which the actuator begins to execute the command and the actual value begins to change.

3.7 maximum overshoot: the largest difference between the actual value and the target value while the drive-by-wire, brake-by-wire or steer-by-wire system carries out the corresponding action. 3.8 steady-state error: the difference between the desired target value and the actual steady-state output of those systems.

3.9 emergency stop device: a control device triggered manually or automatically that makes the chassis-by-wire stop immediately and stay at rest until it is reset.

3.10 event data recorder (EDR): a device or system made up of one or more modules that monitors, acquires and records vehicle data before, during and after events of various kinds. The source is given as GB 39732-2020, 3.2, modified.

3.11 to 3.15 the document also defines maximum driving speed, estimated maximum speed, no load, full load and over-the-air (OTA) upgrading. No load is the state in which no added structure is present apart from the equipment that has to be installed; full load is the total mass when other structures are added to the unladen chassis and it is filled with goods, the loaded total mass not exceeding the maximum permissible total mass of the chassis.

4 General requirements

4.1 The design and manufacture of the low-speed chassis-by-wire shall ensure safe operation, with no unreasonable hazard when it is operated and maintained normally according to the product instruction manual. Components shall comply with the corresponding national standards and be manufactured to drawings and technical documents approved through the prescribed procedure. At least one towing device meeting GB 32087 shall be fixed or installed at the front of the chassis.

4.2 The chassis shall have an emergency stop device or a drive interface for one, and the signal triggered by that device shall be storable in the EDR or uploadable to the vehicle platform. The device shall be installed in a conspicuous position that is easy to operate, shall take priority over the other control devices of the chassis, shall be of the ON/OFF type or of the self-resetting type, and shall be reset manually or automatically by remote control. The emergency stop output signal shall remain valid after the power of the chassis has been removed.

4.3 The chassis shall support the installation of a collision protection device; when an obstacle is struck it shall be able to brake in an emergency, with a trigger force of not more than 50 N. After manual confirmation, the emergency stop state shall be released manually or remotely. Throughout the collision, before and after, the related collision information shall be storable in the EDR or uploadable to the vehicle platform.

4.4 When a manual control device is used, the remote control distance shall be not more than 50 m; beyond 50 m the manual control device shall give an alarm signal. The response time from the issuing of a control command to the start of the corresponding operation by the chassis shall not exceed 100 ms; when control commands are lost the chassis shall stop immediately and hold a static park. When the chassis is in drivable mode and the remote controller has not been operated for more than 1 min, the remote controller shall be unlocked before the chassis can be operated normally again. When the chassis leaves the planned control range of the remote driving system, that system shall give an alarm signal and the chassis shall stop immediately and hold a static park.

4.5 Electrical parts that constitute a hazard shall have fixed guards and enclosures which, during normal operation or standstill, can be removed or opened only with a tool. For the class B voltage defined in GB 18384-2020, the waterproof rating required of components depends on the installation zone with the vehicle fully laden, and the protection degrees shall satisfy GB/T 4208: not lower than IPX3 for the battery and electrical compartment, not lower than IPX4 for high-voltage parts under the chassis that are shielded, and not lower than IPX7 for high-voltage parts under the chassis that are not shielded. Simulated washing and simulated wading tests shall be run according to 7.6, and after each test, with the chassis still wet, the insulation resistance shall be measured by the method of GB 18384-2020, 6.2.1 and shall meet 5.1.4.1 of that standard.

4.6 The chassis shall have interfaces for mounting lighting and light-signalling devices; key lamps shall have a self-check function and shall support the uploading of their switching state and command control. A note lists the key lamps as headlamps, direction indicators, stop lamps, reversing lamps and warning lamps. An interface for mounting an audible signalling device shall also be provided.

4.7 The instruction manual shall state the purpose and scope of application of the product and, according to its features and needs, give the main structure, performance, model, specification and the correct methods of lifting and transport, installation, use, operation, repair, maintenance and storage, together with the measures protecting the operator and the product. It shall give safety warnings on matters of safety, and shall cover safety and accident handling (protective devices and precautions, procedures and methods when a fault occurs, emergency measures for sudden events) and maintenance and repair (daily maintenance and calibration, maintenance during operation, inspection intervals, normal repair procedures and maintenance during long periods out of use).

4.8 The chassis shall carry warning texts and safety reminder signs complying with GB 24943. It shall carry a product nameplate reliably fixed in a visible position, whose content includes but is not limited to the identification number, manufacturer, country of manufacture, chassis mass, maximum permissible load, rated capacity of the traction battery and month and year of manufacture; the performance of the nameplate shall meet GB/T 25978. The chassis shall have a unique chassis identification number and unique serial numbers for the drive motor and the traction battery, whose content and composition shall satisfy GB 16735; the chassis identification number shall be stamped on a visible part of the outer side of the frame, and the recorded characteristic information shall not be permitted to be altered or to be read by tools obtainable on the market.

5 General technical requirements

5.1 The chassis shall pass over certain specific terrain as required by its design, such as vertical obstacles, horizontal trenches and wading pools. Under non-accelerating conditions, whether unladen or laden, it shall be tested by the method of 7.4 and shall be able to pass at constant speed over a speed hump 5 cm high and 30 cm wide.

5.2 Tested by the method of 7.2, the lateral deviation of the chassis shall be less than 2 m.

5.3 The chassis shall stay normal when used, transported and stored under the environmental conditions given in table 1; where it has to work in special environments, the environmental conditions are laid down separately by the user. Table 1 fixes ambient temperature, relative humidity and atmospheric pressure for operating and for storage conditions. The operating temperature range runs from minus 20 degrees Celsius to 55 degrees Celsius and the storage range from minus 25 degrees Celsius to 55 degrees Celsius; relative humidity in operation is not more than 50 % at 40 degrees Celsius and not more than 90 % at 20 degrees Celsius, and in storage not more than 95 % at 40 degrees Celsius. The table also fixes an atmospheric pressure range, but in the extracted text that value stands in a single cell and cannot be assigned with certainty to the operating column, the storage column or both, so it is not reported here.

5.4 The functional design of each safety-related system shall meet overall requirements covering: documents describing the functional concept of the chassis, its internal and external interfaces, potential failure risks and safety measures, with a list of functional descriptions; evidence that a safety analysis was carried out at the design stage to identify potential sources of failure; an explanation of how the working state of the chassis is checked in normal operation and in failure modes; and the definition of the scope of the item, with a block diagram of its architecture and interfaces and a detailed list including hardware and software version numbers. A functional safety risk analysis shall be carried out according to the application scenario, covering the likelihood of hazardous events, a functional safety integrity level rating, safety risks under fault-free conditions, the interaction of the chassis with other vehicle systems, and a hazard analysis and risk assessment (HARA) determining the automotive safety integrity level (ASIL) of hazardous events.

5.4 (continued) The safety goals shall include the safe and reasonable execution of all dynamic driving tasks within the designed operating range without unreasonable risk to road users and in compliance with traffic rules, and the assurance that the chosen safety strategy does not impair safe operation under faulty or fault-free conditions. Table 2 lists four hazards of the electrical and electronic systems with their safety goals: unintended lateral motion, unintended loss of control of lateral motion, unintended longitudinal motion, and unintended loss of control of longitudinal motion; for the two loss-of-control entries the goal is to ensure the ability of the driving automation system or control device to control the motion concerned, with the corresponding control force meeting the safety metric. Verification measures comprise functional tests in the fault-free state, the simulation of internal component faults by applying corresponding signals to chassis components, and the retention of documentary records of the risk analysis and of the verification. During operation the safety-related systems shall be able to upload operating status information in real time over a CAN network or a wireless network, namely operating mode information, the functional state and fault information of non-motion actuating parts such as sensors and lamps, and the state and fault information of the steering, drive, battery and braking systems.

5.5 The chassis shall have technical measures protecting electronic systems, components and functions against network threats, with identity authentication and data encryption security management, so that data collection, processing and exchange cannot be obtained or altered illegally. If it has a software upgrade function, the security and reliability of the data upgrade shall be safeguarded. It shall be fitted with an EDR able to record data such as the running speed and braking state of the chassis when a collision or other specific accident occurs.

5.6 Electromagnetic compatibility requirements and test methods shall comply with GB 34660 and GB/T 18387.

5.7 The chassis shall be able to handle faults in grades, with at least warning, power (speed) limitation and stopping. After a fault has been repaired it shall support reset operations to release the driving restriction. For faults that prevent the chassis from moving automatically, where the effect on the chassis controller is small and the fault cannot be repaired at once, a corresponding fault bypass function shall be provided so that temporary maintenance and moving of the vehicle are possible.

5.8 The traction battery pack or system shall meet GB 38031 for safety and GB/T 31486 for electrical performance, and the charging interface shall meet GB/T 20234.1. Where battery swapping is used, after running 15 000 km as required by GB/T 40032-2021, 4.2.1, after 5 000 clip-type and 1 500 bolt-type swapping operations as required by 4.2.2 of that standard, and after the simulated washing and wading test of its 4.2.3, none of the following failure modes shall appear: inability to swap because of interface or mechanism problems; damage to the interface or mechanism caused by swapping; body deformation or loosening of the battery box; loosening or dropping of swapping mechanism parts; damaged sealing or leakage of water or fluid; faults of the interface and mechanism while driving. Circuits involving CAN communication shall meet the CAN bus physical layer requirements of GB/T 36048. Battery management shall meet GB/T 38661-2020, 5.3. When the supply system voltage does not meet the operating voltage requirement, the chassis shall acquire that information and upload it to the control system.

5.9 The chassis shall be fitted with an open API interface and a CAN communication interface, and with a standardised protocol and interface for communication with the driving automation system or other control devices, supporting the CAN 2.0A and CAN 2.0B protocols. The communication protocol shall define at least: basic information (gear, state of charge, fault information, vehicle speed, wheel speed, longitudinal acceleration, lateral acceleration and yaw rate where fitted, tyre pressure, mileage); chassis operating state, ready or not ready; control mode, remote control, automated driving or no control; requests to take over automated driving; drive information (motor speed, motor torque); braking information (braking torque or braking pressure, opening command, feedback of braking torque or pressure, actual braking opening, parking command, parking state value, redundant braking state where fitted); and steering information (target steering angle, current steering angle, wheel-end angle where fitted, steering torque value, motor speed, motor current, steering system fault state). A fault diagnosis interface meeting GB/T 34589 shall be provided. If the chassis has an OTA function, background OTA shall be supported in the non-working state; a two-way authentication mechanism shall be used between the chassis end and the cloud server, the data transmission of the upgrade package shall be encrypted, and where the upgrade fails the chassis shall roll back automatically to the previous version. Detailed logs shall be kept in the cloud and detailed version information at the chassis end.

6 Requirements for by-wire systems

6.1 For the drive-by-wire system, the 30 min maximum speed shall be tested by the method of GB/T 18385 and the speed shall match the estimated 30 min maximum speed within plus or minus 5 %; if during the test the speed does not reach 95 % of the estimated value, the test is repeated. Acceleration performance shall meet the needs of the application scenario. The drive system shall have at least one of the accelerator, torque, acceleration and speed control modes; when the accelerator interface is used the chassis responds to the target accelerator opening, when the torque interface is used to the target torque, when the acceleration interface is used to the target acceleration, and when the speed interface is used to the target vehicle speed.

6.1 (continued) The response capability of the drive system is fixed as follows: with accelerator control, the step response time from 0 % to 100 % accelerator opening not more than 100 ms, maximum overshoot not more than 10 % and steady-state error not more than 5 %; with torque control, step response time not more than 200 ms, maximum overshoot not more than 10 % and steady-state error not more than 5 %; with acceleration control, step response time not more than 250 ms, maximum overshoot not more than 10 % and steady-state error not more than 5 %; with speed control, step response time not more than 300 ms, maximum overshoot not more than 10 % or 1 km/h and steady-state error not more than 5 % or 0.5 km/h. When fully laden the gradeability shall be not less than 20 % without stopping or rolling back during the climb, and hill start on a 20 % gradient shall be possible.

6.2 The chassis shall have a service braking system and a parking braking system meeting the performance requirements, and during braking it shall not deviate, skid or lose steering. The service braking road test is run under the conditions of table 3 by the method of 7.3, and the performance shall satisfy formula (1). In the legend of that formula S is the braking distance in metres and v0 is the initial braking speed in kilometres per hour; the equation itself is damaged in the extracted text and is not reconstructed here. Table 3 fixes the minimum width of the test lane as a function of vehicle width: for a vehicle width below 2.5 m the lane is 2.5 m wide, and for a width of 2.5 m or more the lane is the vehicle width plus 0.5 m.

6.2 (continued) The parking braking device shall be able to hold a vehicle carrying the chassis stationary, unladen or fully laden, on a 20 % gradient in both the forward and the reverse direction with a tyre-to-road adhesion coefficient of not less than 0.7, for not less than 5 min. Parking braking shall have a working-state feedback function and a parking brake signal interface. The chassis shall provide a braking pressure or deceleration control interface so that closed-loop control of the braking system under different loads is supported: with the braking pressure interface it shall respond to and follow the target braking pressure, with the deceleration interface the target deceleration, and it shall be fitted with an acceleration sensor or be able to output a wheel speed signal. With braking pressure control the braking step response time shall be not more than 200 ms and the overshoot not more than plus or minus 0.3 MPa or plus or minus 10 %; with deceleration control the step response time shall be not more than 250 ms and the overshoot not more than plus or minus 0.5 m per second squared or plus or minus 10 %.

6.3 The steer-by-wire system shall support closed-loop control of steering angle or position; while running normally on a flat, dry and clean road it shall not float, shimmy, judder or deviate when no steering command is given; the symmetry between the maximum left and the maximum right wheel steering angles shall be greater than 95 %; a steering mechanism angle or position signal and a steering motor speed signal shall be provided; an abnormality detection mechanism shall be present that executes safety measures within 100 ms when a steering fault is detected and can report the corresponding fault code; and the design shall give the chassis some weak understeer to improve running safety. For response capability, the wheel-end angle resolution shall be not more than 0.3 degrees, the response time of the steering system not more than 200 ms, and with the whole vehicle unladen and stationary, when the wheel-end target angle turns from 0 degrees to plus or minus 25 degrees, the steering angular velocity in the region between 20 % and 80 % of the target angle shall be not less than 15 degrees per second, the maximum overshoot not more than 1 degree and the steady-state error not more than 0.6 degrees.

7 Test methods

7.1 Unless otherwise specified, all tests are run on flat, hard, dry and clean concrete or asphalt roads with an adhesion coefficient of not less than 0.7 and a wind speed of not more than 3 m/s.

7.2 For the straight-line running stability test the chassis under test runs unladen at a constant speed of 5 km/h plus or minus 1 km/h for 100 m and stops at the end point, and the lateral deviation is measured; the test is repeated three times there and back. If the chassis cannot reach that speed, the test is run at the maximum design speed.

7.3 For the service braking test the chassis runs in a straight line at a constant speed over a stretch of road at 5, 10, 15, 20 and 25 km/h, each plus or minus 1 km/h; on reaching the braking line the emergency stop device is pressed and the distance S between the braking line and the stopping line of the chassis is measured. The test is repeated three times at each speed, both unladen and fully laden. If the chassis cannot reach the speeds required, the maximum design speed is divided into three speed values for the calculation.

7.4 For the speed hump trafficability test a speed hump meeting the test requirements is placed on the test road and the chassis passes over it at 5 km/h and at 10 km/h, each plus or minus 1 km/h; whether it passes smoothly is recorded both unladen and fully laden. If those speeds cannot be reached, the test is run at the maximum design speed.

7.5 The gradient tests comprise a climbing test, a gradient braking and parking test and a gradient power-off parking test. In the climbing test the chassis climbs at 5 km/h plus or minus 1 km/h a gradient meeting the requirement (not less than 20 % when fully laden) and shall not stop or roll back. In the gradient braking and parking test it runs uphill and downhill on such a gradient and, after the brake button is pressed, shall stay fixed for not less than 5 min and shall then be able to start again on the gradient. In the power-off parking test the vehicle stops after the brake button is pressed, the power is cut off, and the chassis shall stay fixed for not less than 5 min; after the power is switched on again it shall run normally.

7.6 For simulated washing the whole chassis is sprayed with clean water through the IPX5 hose nozzle of GB/T 4208 at a flow of 12.500 L/min plus or minus 0.625 L/min, in all possible directions towards all boundary lines, for not less than 3 min, with the nozzle 3.0 m plus or minus 0.5 m from the boundary line. For simulated wading the chassis runs at 10 km/h plus or minus 1 km/h for at least 300 m in a pool 100 mm deep; if the pool is shorter than 300 m the test is repeated until the cumulative wading distance is not less than 300 m.