Explore SBW functional safety objectives and safety tools
The topic of functional safety is actually a bit big. The following assumes that the reader has a certain understanding of the functional safety of EPS. It is just a sneak peek about the new changes in SBW compared with EPS. After importing the remote control steering (for the time being, only consider the SBW of this stage of L2, whether it is SBW or EPS above L3, its functional safety objectives are significantly different from L2), there are two new Hazard that must be considered:
The actuator on the steering gear side does not correctly rotate the wheel to the target corner
The reasons for this may vary, such as steering column angle sensor failure, rack position sensor failure, steering motor failure, steering control controller failure, etc.
Corresponding safety means: In the case of corresponding failure, if the actuator on the steering side can work normally to control the output torque of the motor, then the safety measure is to suck the clutch and perform the EPS backup function by the actuator on the steering side. The entire system is equivalent to a set of PEPS or REPS;
If the actuator on the steering side cannot control the output torque of the motor, the safety measure is to separate the suction and the suction, and the EPS backup function is performed by the steering column side controller. The whole system is equivalent to a set of C-EPS.
If a more serious fault occurs and neither of the two actuators can properly control the motor, it can only be switched to mechanical steering.
The torque feedback mechanism on the steering column side does not provide the torque feedback correctly, causing the driver to malfunction.
The reason may be that the signal used to estimate the driving state of the vehicle is lost or incorrect, the steering column side motor and the controller itself are faulty, etc.
The safety method is to suck the clutch and perform the EPS backup function by the actuator on the steering side, and the whole system is transformed into a set of PEPS or REPS.
Architecture
Since it is a Conception design, for the time being, it does not consider the implementation of the control strategy in the embedded controller, and uses a rapid control prototype (RCP) to achieve its function.
Motor and GearBox assembly: The steering gear side motor is basically the same as EPS. If the steering column side motor does not realize its EPS backup function, it only needs to provide a torque feedback of 0-5Nm to the driver. The limit speed of the steering wheel is also 1000 ° / s (about 170 rpm), so you can choose a smaller motor than the EPS power and a smaller GearBox reduction ratio.
Two motor controllers: only receive motor torque command from RCP, execute torque closed loop
AS two: one on the column and the steering gear
Software function allocation
VehicleDynamic model: mainly based on vehicle speed, wheel speed, yaw rate, rack torque, tire deflection angle, etc., can be measured on the vehicle, using several state observers to obtain such as rack force, centroid side angle , the tire slip angle, etc. can not be obtained through direct measurement but the key signals required by the control strategy.
The simplified implementation method is the use of BicycleModel and simplified steering model. The paper "Steer-by-Wire for Vehicle State Estimation and Control" published by AV Yi 2004 (Advanced Vehicle Control) by Stanford University has a detailed formula derivation and implementation process.
Target position calculation: In the steer-by-wire steering, the target rotation angle of the rack and the steering wheel angle are not simply proportional correspondences, one of which can realize the active steering function of the variable steering ratio; in addition, the vehicle is judged according to the dynamic parameters calculated by the Vehicle Dynamic model. Whether it is in the UnderSteer or Oversteer state, and then adjust the target steering angle to play the role of DSR.
Feedback torque calculation: According to the VehicleDynamic model and the steering column model, the control servo motor provides a force feedback to the driver. This part requires the simulation of the real hand (the intermediate position sense, the steering force build gradient, the condition information feedback, etc.) without any real physical connection between the steering column and the steering gear. Whether it is strategy design or parameter calibration, it is undoubtedly It takes a lot of technical difficulty to work hard.
Power Meter is a monitoring and testing instrument which determines the power consumption of a connected appliance and the cost of the electricity consumed.
Built-in 3.6V rechargeable Batteries ( . The purpose of the batteries is to store the total electricity and memory setting
Resetting
If an abnormal display appears or the buttons produce no response, the instrument must be reset. To do this,
press the RESET button.
Display Mode
Entire LCD can be displayed for about 1 minute and then it automatically gets into Model. To transfer from
one mode to the other, press the FUNCTION button.
Mode 1: Time/Watt/Cost Display Display duration(how long) this device connect to power source.LCD on first line shows 0:00 with first two figures mean minutes(2 figures will occur while occur at 10 min) and the rest shows seconds. After 60mins, it displays 0:00 again with first two numbers meas hour(2 figures will occur at 10hours)and the rest shows minutes. The rest can be done in the same manner which means after 24 hours, it will re-caculate. LCD on second line displays current power which ranges in 0.0W 〜 9999W. LCD on third line displays the current electricity costs which ranges in O.Ocost 〜 9999cost. It will keep on O.OOcost before setting rate without other figures.
Mode 2: Time/Cumulative electrical quantity Display Display duration(how long) this device connect to power source.
LCD on first line shows 0:00 with first two figures mean minutes(2 figures will occur while occur at 10 min) and the rest shows seconds. After 60mins, it displays 0:00 again with first two numbers meas hour(2 figures will occur at 10hours)and the rest shows minutes. The rest can be done in the same manner which
means after 24 hours, it will re-caculate. LCD on second line displays current cumulative electrical quantity which ranges in 0.000KWH 〜 9999KWH without other figures. LCD on third line displays"DAY"- "1 'Will be showed on numerical part(the other three figures will be showed at carry) which means it has cumulated electrical quantity for 24hours(one day). The rest can be done in the same manner untill the maximal cumulative time of 9999 days.
Mode 3: TimeA^bltage/Frequency Display LCD on first line displays the same as Mode 1 dones. LCD on second line displays current voltage supply (v) which ranges in 0.0V 〜 9999V .LCD on third line displays current frequency (HZ) which ranges in 0.0HZ 〜 9999Hz without other figures.
Mode 4: Time/Current/Power Factor Display LCD on first line displays the same as Mode 1 dones.LCD on second line displays load current which ranges in 0.0000A 〜 9999A. LCD on third line displays current power factor which ranges in 0.00PF 〜 LOOPF without other figures.
Mode 5:Time/Minimum Power Display LCD on first line displays the same as Mode 1 dones. LCD on
second line displays the minimum power which ranges in 0.0W 〜 9999W. LCD on third line displays character of "Lo" without other figures.
Mode 6: Time/Maximal Power Display LCD on first line displays the same as Mode 1 dones. LCD on second line displays the maximal power which ranges in 0.0W 〜 9999W. LCD on third line displays character of "Hi" without other figures.
Mode 7: Time/Price Display LCD on first line displays the same as Mode 1 dones. LCD on third line displays the cost which ranges in O.OOCOST/KWH 〜 99.99COST/KWH without other figures.
Overload Display: When the power socket connects the load over 3680W, LCD on second line displays the''OVERLOAD[ with booming noise to warn the users, (selectable choice)
Supplemental informations:
1: Except [OVERLOAD[ interface, LCD on first line display time in repitition within 24hours.
2: LCD on first line, second line or third line described in this intruction take section according to two black lines on LCD screen. Here it added for clarified purpose.
3. Mode 7 will directly occur while press down button "cost".
4. [UP"&"Down" are in no function under un-setting mode.
Setting Mode
1. Electricity price setting
After keeping COST button pressed lasting more than 3 seconds(LCD on third line display system defaults price, eg O.OOCOST/KWH ),the rendered content begins moving up and down which means that the device
has entered the setting mode. After that, press FUNCTION for swithing , then press "UP"and "DOWN" button again to set value which ranges in OO.OOCOST/KWH 〜 99.99COST/KWH. After setting all above, press COST to return to Mode7 or it will automatically return to Mode7 without any pressing after setting with data storage.
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