
EPB功能安全笔记(5):EPB系统软件接口定义
本文要点
在上文中基于VDA 305对EPB系统架构进行了阐述,并对系统架构中的各个软件模块的功能做了说明。其中,绿色部分属于Brake Assy,包括电机控制软件(PBC, parking brake controller)和制动卡钳;蓝色部分属于ESC Assy,又称Brake Host,提供EPB ECU和供电电源、CAN 通讯接口、硬线接口等外围设备和EPB宿主软件。Brake Assy和ESC Assy一起构成完整的EPB系统。
EPB系统架构,绿色:Brake Assy; 蓝色:ESC Assy
定义EPB系统架构是为了接下来分析技术安全要求,而技术安全要求最终需要落实到具体的交互信号上的。从这个角度上看,上图所示只是一个基于EPB功能需求初步定义的框架,框架中各个软件模块间的接口还需要明确定义。所以本文将对这部分内容进行补充说明。
1.软件接口定义
从EPB系统框架图中可以看出,确定各个软件模块间的接口,本质上就是确定Brake Assy的PBC软件和ESC Assy的Host软件间的接口。下面将从这个角度出发定义PBC软件和ESC Host软件的接口。
1.1.激活请求接口(Actuation Request Interface)
激活请求接口如下图所示,其中包含了SSM模块与PBC之间的双向通讯信号。
PBC与Host之间的激活请求接口
接口描述
Interface | Task and Interface Content |
PbcInApplyReleaseRequest | SSM → PBC: Transmitting EPB requests to the PBC. · None · ParkApply (apply request in “parking situation”) · HoldApply (apply request in “stopping situation”) · RollerbenchApply (apply request for the technical inspection of the parking brake function) · Release · DynamicApply · PadAdjustment (brake pad wear adjustment) · EmergencyParkApply (apply request in “emergency situation”) · HapPreparation (actuation request to achieve an open, for a HAP situation optimized, condition) |
PbcInRollerbenchActive | SSM → PBC: Transmitting a detected roller bench situation. In this situation, the Brake Assy will react to a RollerbenchApply request with a Brake Assy specific roller bench function. Upon discontinuation of the roller bench situation, an active roller bench function is terminated by release of the EPB. |
PbcOutActuatorState (L/R) | PBC → SSM: Transmitting the current logical brake state for the individual wheels. A distinction is made between final states and transition states. Final states: · ParkApplied (parking situation, vehicle is held by EPB) · Released · Unknown (final state not defined) · HoldApplied (stopping situation, vehicle held by EPB) · CompletelyReleased Transition states: · Applying (electromechanical locking of the brake in progress) · Releasing (electromechanical opening of the brake on progress) · HapPrepared (the park brake is in an open, for a HAP situation optimized, condition) |
PbcOutPadAdjustmentRequest | PBC →SSM: The PBC informs SSM about the necessity of a PadAdjustment. As soon as possible, SSM will based on this information trigger a PadAdjustment request by sending PbcInApplyReleaseRequest = PadAdjustment. · NotRequested · Requested |
PbcInDriveAwayIntentionIndication | SSM →PBC: Indication to PBC that a drive off situation is likely to happen. The detection conditions have to be defined project specifically. · NotIndicated · Indicated |
1.2.执行机构控制接口(Actuator Control Interface)
执行机构控制接口如下图所示,其中包含了EPB硬件驱动模块与PBC之间的双向通讯信号。
PBC与Host之间的执行机构控制接口
接口描述
Interface | Task and Interface Content |
PbcInMotorCurrent (L/R) | EPB HW Driver Control → PBC: Transmitting the currently measured motor current of the parking brake actuator upon activation of the parking brake actuators. |
PbcInMotorVoltage (L/R) | EPB HW Driver Control → PBC: Transmitting the currently measured voltage of the parking brake actuators at the motor terminals of the ECU. |
PbcOutActuatorState (L/R) | EPB HW Driver Control → PBC: Transmitting the current logical brake state for the individual wheels. A distinction is made between final states and transition states. |
PbcInMotorDriverSupplyVoltage | EPB HW Driver Control → PBC: Transmitting the supply voltage currently measured |
PbcInHostAvailability (L/R) | EPB HW Driver Control→ PBC: Transmitting the current availability of the electric supply lines2 of the HOST for the respective side. This signal gives feedback about which basic functionality of the EPB hardware driver control is still available. · None · Apply · Release · ApplyAndRelease |
PbcInMotorDriverState (L/R) | EPB HW Driver Control → PBC: Transmitting the switching state of the EPB hardware driver control currently being executed · None (parking brake actuators in idle mode, passive output stage) · Apply · Release · Stop (parking brake actuators in braking mode, active output stage in short circuit of the parking brake actuators without provision of all electric parking brake actuator signals) · FreeRun (parking brake actuators in free run mode, active output stage with provision of all electric parking brake actuator signals) |
PbcInPowerSupplyState | EPB HW Driver Control → PBC: Transmitting the current power supply state to the PBC. · Normal · Limited (definition of “limited” and the system reaction are to be specified by the OEM to the ESC Assy OES and Brake Assy OES) |
PbcOutMotorCommand (L/R) | PBC →EPB HW Driver Control: Transmitting the current actuation request to the EPB hardware driver control. · None (parking brake actuators in idle mode, passive output stage) · Apply · Release · Stop (parking brake actuators in braking mode, active output stage in short circuit of the parking brake actuators without provision of all electric parking brake actuator signals) · FreeRun (parking brake actuators in free run mode, active output stage with provision of all electric parking brake actuator signals) |
1.3.液压制动支持接口(Hydraulic Pressure Support Interface)
在一些机械卡钳制动力不足以保证驻车的特殊情况下,PBC模块会请求ESC建立液压力支持静态驻车。值得一提的是,车辆静止是ESC响应液压制动支持请求的前提条件,ESC的SSM模块会监控车辆状态。液压制动支持接口如下图所示,其中包含了ESC建压模块与PBC之间的双向通讯信号。
PBC与ESC建压模块之间的液压制动支持接口
接口描述
Interface | Task and Interface Content |
PbcOutHpsRequest | PBC → ESC Control & Actuator: Transmitting the request for hydraulic support from the parking brake actuators - None - Normal Pressure Gradient - Maximum Pressure Gradient |
PbcOutHpsPressure | PBC → ESC Control & Actuator: Transmitting the current pressure request in the EPB brakes as absolute pressure for the hydraulic support to achieve safe vehicle holding. |
PbcInHpsAcknowledge | ESC Control & Actuator → PBC: Confirming that the pressure requested by the PBC via the signal PbcOutHpsPressure is achieved by the ESC Assy. |
PbcInHpsAvailability | EPB Control & Actuator → PBC: Transmitting the current availability of the hydraulic actuator. |
1.4.车辆环境数据接口(Environmental Data Interface)
车辆环境数据来自三个方面:
- ESC系统自带的传感器
- ESC从其他ECU接收的信息
- ESC软件的计算的信息
ESC Host将为Brake Assy提供轮速、纵向加速度、主缸压力等信息。车辆环境数据接口如下图所示,其中包含了ESC建压模块与PBC之间的单项向通讯信号。
PBC从ESC Host接收车辆环境信号
接口描述
Interface | Task and Interface Content |
PbcInLongAcceleration | Environmental Data → PBC: Measured longitudinal acceleration of the chassis. |
PbcInWheelSpeed (FL/FR/RL/RR) | Environmental Data → PBC: Detected pulses of the wheel rotary speed sensor. |
PbcInVehicleAmbientTemperatu re | Environmental Data → PBC: Measured ambient temperature of the vehicle. |
PbcInMasterCylinderPressure | Environmental Data → PBC: Measured signal of the pressure sensor at the master cylinder. |
PbcInWheelPressure (FL/FR/RL/RR) | Environmental Data → PBC: Estimated (modeled) wheel pressure of the respective wheel brake. |
PbcInWheelPressureReliability (FL/FR/RL/RR) | Environmental Data → PBC: Additional information on the accuracy of the estimated (modeled) wheel pressure of the respective wheel brake. · Reliable · NotReliable |
PbcInEngineCranking | Environmental Data → PBC: Information that vehicle engine is in cranking phase. · NoEngineCranking · EngineCranking · EngineCrankingUnavailable · EngineCrankingInvalid |
PbcInMileage | Environmental Data → PBC: Current mileage of the vehicle. |
PbcInPbcSleepTime | Environmental Data → PBC: Duration between ‘PBC Exit’ (last call) and ‘PBC Init’ (first call e.g. in new ignition cycle) of the PBC. |
1.5.诊断接口(Diagnostic Interface)
为了确定Brake Assy的组件始是否于正常状态,ESC Host会给PBC发送诊断请求,然后PBC再将诊断结果反馈给ESC Host。诊断接口如下图所示,其中包含了ESC Host诊断模块与PBC之间的双项向通讯信号。
PBC与ESC Host的诊断接口
接口描述
Interface | Task and Interface Content |
PbcInDiagOperationMode | Diagnosis→ PBC: This signal provides information about which mode the PBC shall adopt. · Normal Mode“ · „Diagnosis Mode“ (HOST informs PBC, about System is in Diagnose Mode.) Possible additional modes may include transport mode, factory mode, etc. |
PbcInDiagRequest | Diagnosis→ PBC: Diagnostic request for Brake Assy specific diagnostic functions: · OpenBrakeRearLeft, OpenBrakeRearRight, OpenBrakeBoth, · CloseBrakeRearLeft, CloseBrakeRearRight, CloseBrakeBoth, · TouchBrakeRearLeft, TouchBrakeRearRight, TouchBrakeBoth, · StepCloseRearLeft StepCloseRearRight StepCloseBoth · AssemblyCheck, · EnterMaintenanceMode, · ExitMaintenanceMode · DataResetA (Reset of PBC EEPROMData. Definition to be defined within application project) · DataResetB (Reset of PBC EEPROMData. Definition to be defined within application project) · FactoryReset (Reset of all PBC EERPOM Data: Area 1 till 3) |
PbcInHOSTSoftwareVersion | Diagnosis→ PBC: Provision of current HOST software version. |
PbcOutDiagRequestStatus | PBC →Diagnosis: Status feedback about the diagnosis request from Brake Assy specific diagnostic functions: · Idle · Started · Running · Done · Error |
PbcOutDiagRequestAcknowledge | PBC →Diagnosis: Feedback about the diagnosis request from Brake Assy specific diagnostic functions: · OpenBrakeRearLeft, OpenBrakeRearRight, OpenBrakeBoth, · CloseBrakeRearLeft, CloseBrakeRearRight, CloseBrakeBoth, · TouchBrakeRearLeft, TouchBrakeRearRight, TouchBrakeBoth, · StepCloseRearLeft StepCloseRearRight StepCloseBoth · AssemblyCheck, · EnterMaintenanceMode, · ExitMaintenanceMode · DataResetA (Reset of PBC EEPROM Data. Definition to be defined within application project) · DataResetB (Reset of PBC EEPROM Data. Definition to be defined within application project) FactoryReset (Reset of all PBC EERPOM Data: Area 1 till 3) |
PbcOutDiagBrakeTemperatureLeft | PBC →Diagnosis: Provision of Brake Assy specific diagnosis relevant information: brake temperature left |
PbcOutDiagBrakeTemperatureRight | PBC →Diagnosis: Provision of Brake Assy specific diagnosis relevant information: brake temperature right |
PbcOutDiagActuationCounterLeft | PBC →Diagnosis: Provision of Brake Assy specific diagnosis relevant information: actuation counter left |
PbcOutDiagActuationCounterRight | PBC →Diagnosis: Provision of Brake Assy specific diagnosis relevant information: actuation counter right |
PbcOutDiagAchievedClampForceLeft | PBC →Diagnosis: Provision of Brake Assy specific diagnosis relevant information: clamping force left |
PbcOutDiagAchievedClampForceRight | PBC →Diagnosis: Provision of Brake Assy specific diagnosis relevant information: clamping force right |
PbcOutPbcSoftwareVersion | PBC →Diagnosis: Provision of current version of PBC software. |
1.6.数据存储接口(Data Storage Interface)
数据存储接口的任务是保护PBC内部数据的时间超过一个功能周期,比如保证下次启动ECU时要能正确读取到上一次关闭ECU时的一些关键数据(EE存储)。存储数据的内容由Bake Assy的供应商定义,ESC Assy的供应商只负责正确存储。数据存储接口如下图所示,其中包含了ESC Host存储模块与PBC之间的双项向通讯信号。
PBC与ESC Host的数据存储接口
接口描述
Interface | Task and Interface Content |
PbcInDataStorageValid(1…3) | Persistent Data Storage→ PBC: Validity information from the HOST to the Brake Assy. Selective for each of the three specified ranges of stored data from the nonvolatile rewritable memory. |
PbcInUnexpectedPowerdown | Persistent Data Storage→ PBC: Information from the HOST to the PBC on whether the HOST system has not been properly shut down (e.g.unexpected power failure) |
PbcInVariantItem (1…n) | Persistent Data Storage→PBC: Coding items 1 to 64 (coding commands from the HOST to the PBC). The HOST does not have to have any knowledge of the content of the data. |
PbcInDataStorageRead | PBC →Persistent Data Storage: Provision of Brake Assy specific data for storage in the non-volatile rewritable memory. |
PbcOutDataStorageRequest | PBC →Persistent Data Storage: PBC request to store memory area 3. · NoStorageRequest · StorageRequest |
1.7.系统模式管理接口(System Mode Management)
系统模式管理接口如下图所示,用来监控并请求PBC函数被调用的状态(‘PBC Init’, ‘PBC Cyclic’and ‘PBC Exit’)。
PBC与ESC Host的系统模式管理接口
接口描述
Interface | Task and Interface Content |
PbcOutEcuPowerLatchRequest | Request from PBC to HOST that the PBC shall continue to be called cyclically. If the PBC sends this request, the HOST shall not terminate the cyclical call. |
PBC模式切换示意图
1.8.故障管理接口(Fault Management Interface)
故障管理接口的定义遵循ISO 14229-1 and Autosar 4.0。PBC自身不包含故障管理模块,但是包含所有必要的PBC故障监控逻辑。PBC故障监视器将故障发送给ESC HOST故障管理模块进行统一处理,由Host来做出正确的降级控制。
故障管理接口如下图所示。
PBC与ESC Host的故障管理接口
接口描述
Interface | Task and Interface Content |
PbcInFaultRecoveryRequest (1…n) | Fault Management → PBC: Request for the relevant monitor to execute the recovery request. |
PbcOutFaultStatus (1...n) | PBC →Fault Management: Current status of the individual fault monitors. |
1.9.人机交互接口(HMI)
Brake Assy通过HMI界面显示的信号将发给ESC Host由Host转发。发送的信号由具体项目需求来定义,VDA305不给出推荐。
PBC将需要提醒驾驶员的Brake Assy状态信息发给ESC Host
接口描述
Interface | Task and Interface Content |
PbcOutOutOfSpecMsg | PBC →HMI: Information signal that the current vehicle state (e.g. brake temperature, gradient, etc.) lays outside the range specified for the parking brake. |
1.10.驻车支持接口(Parking Support Interface)(可选)
根据项目需要,PBC可以通过驻车支持接口控制除卡钳外的其他驻车机构,该请求将通过ESC Host的SSM模块进行转发。
PBC请求控制其他驻车机构
接口描述
Interface | Task and Interface Content |
PbcOutParkSupportRequest | PBC →SSM: PBC à SSM: PBC can request external support to hold the vehicle. · NotRequested · Requested |
2.基于VDA 305的EPB系统描述
下篇预告
本文基于EPB系统初步的系统框架,在框架中定义的各个模块的功能基础上,细化了各个模块间的信号接口,得到一个更加具体的EPB系统架构。
下一期将基于EPB系统框架以及接口定义,以前文分析确定的Safety Goal(见下)为目标,具体阐述如何分配和定义技术安全要求。
Safety Goal:EPB应避免错误建压而造成过高的减速度
ASIL: C
FTTI:600ms
safe state: EPB shut down and warn driver
safety margin: deceleration < -3m/ss
本文转载自:焉知智能汽车
