146
147 is also possible to connect it to a vacuum pump, to generate an additional force, thanks to the vacuum.
Figure 4.5 – Vacuum attack
In the vehicle, the brake booster is connected either to the intake manifold (in the case of a petrol engine) or to a small vacuum pump (in the case of a Diesel engine, because the vacuum in the intake manifold is not high enough). For the use of the test rig, the use of a vacuum pump is not necessary required, because simply generating more force with the actuator will suffice.
Following the brake booster, the tandem master cylinder (TMC) is mounted, highlighted in yellow in Figure 4.4, from which the power supplies go out to the two circuits. In fact, by law, the braking system must be split, in the sense that only one power line can not slave all four calipers. For this reason, two lines are made which feed only two clamps each. In general, one line feeds the front left caliper and the rear right caliper and the other line supplies the remaining two callipers. This is necessary in case of failure, in order to have the possibility to stop the vehicle. Two pressure sensors are mounted on the outlet pipes of the tandem master cylinder, and are highlighted in the following figure.
Figure 4.5 – TMC pressure sensors
148
The ABS control unit is then installed. The two tubes of the TMC arrive in it and then four tubes that go to the calipers come out.
Figure 4.7 – ABS and CAN connection
Next to the ABS control unit, there is the connection to the Controller Area Network (CAN) of the vehicle (Figure 4.7). It is important to know that the ABS control unit not only receives the information necessary for its operation (wheel angular speeds, pressure in the callipers, etc.) but also requires other information that can be defined as “sign of life” of the vehicle. For example, it may be necessary to send information regarding engine revolutions or enter a code that refers to the type of motor installed.
Finally, the four static brake disks are mounted, with their respective calipers.
Figure 4.8 – Front brake disk and caliper. Figure 4.9 – Rear brake disk and caliper.
149 A pressure sensor is mounted on each caliper.
Furthermore, two terminal blocks were also made:
the first is the one that collects the power harnesses. In fact it is equipped with wirings with a larger section.
Figure 4.10 – Power terminal block
The meanings of the individual cables are shown in the following table:
Table 4.1 – Power wiring.
Order Pin Description
1 1 Ground
2 2 Electronic Parking Brake right + 3 3 Electronic Parking Brake right - 4 12 Electronic Parking Brake left - 5 13 Electronic Parking Brake left +
6 30 Generic battery feed
The second it that which collects all the signals of the CAN that must be generated, in order to make the ABS work correctly. To do this, a National Instruments CAN interface module was purchased with a suitable cable mounted on the PXI (which is a computer particularly suited to real-time applications).
150
Figure 4.11 – Signals terminal block
In this case, the cable section is lower than the previous ones. The meaning of each cable is shown in the following table:
Table 4.2 – Signals wiring.
Order Pin Description
1 5 Com – CAN (+) 500k PT (CGW engine side) standard 2 19 Com – CAN (-) 500k PT (CGW engine side) standard 3 11 C – CAN H Electronic Power Steering
4 25 C – CAN L Electronic Power Steering
5 24 Front left wheel sensor (+)
6 7 Front left wheel sensor (-)
7 21 Front right wheel sensor (+)
8 26 Front right wheel sensor (-)
9 22 Rear right wheel sensor (+)
10 37 Rear right wheel sensor (-)
11 39 Rear left wheel sensor (+)
12 23 Rear left wheel sensor (-)
13 27 Brake booster vacuum sensor feed 14 29 Brake booster vacuum sensor return 15 42 Brake pedal normal closed 2nd signal 16 45 Brake booster vacuum pressure signal 17 17 Brake pedal normal closed 1st signal 18 15 Electronic Parking Brake – SW – 6 Backup 19 16 Electronic Parking Brake – SW – 1 20 31 Electronic Parking Brake – SW –3 21 32 Electronic Parking Brake – SW – 6
22 34 VSO signal
23 36 Electronic Stability Control pump – kl15
151 For the description of the signals, it is advisable to request further information directly from Danisi Engineering. At the time of writing there is no further information on the first four signals and the last six in Table 4.2; for this reason the short description given at the moment by Danisi Engineering was reported.
152
Conclusions
The next step will concern the installation of the material provided by National Instruments to interface with the brake test rig. The next objective will be to insert the ABS control unit of the brake test rig inside the Amesim model and verify its operation. Then it can be possible to insert the Amesim model, with the hardware in the loop, inside a Simulink model that interfaces with CarMaker, so as to test its operation in real-time. Clearly all this requires that both Amesim and CarMaker are updated all the vehicle parameters. It is recommended to pay maximum attention to the tire model; the advice is to try to use the same model, in order to correctly insert the same parameters. The same brake test rig can be used to be included in the study of torque vectoring differentials; this technology uses the braking system to vary the driving torque that reaches the drive wheels. This allows the vehicle to reduce under-steering when cornering. Another possible use is to go to study an intelligent brake system, that is an active brake system that stops the vehicle if it senses the presence of an imminent danger, anticipating the intervention of the driver. Finally, one last study is the one concern the recovery of braking energy. Since the car market is pushing a lot on hybrid propulsion, it becomes important to have an efficient braking energy recovery system to effectively charge the batteries. To do this, it could be interesting, going to make the test rig brake disks mobile and study a connection with an electric motor to improve efficiency of the recovery of kinetic energy.
153
Reference
[1] Kirlin C.., “An Introduction to Hardware In the Loop (HIL) Simulation and Its Applications”, International journal of advances in engineering, vol 2, n°1, 2016
[2] https://en.wikipedia.org available in 2018-10-03.
[3] Kleijn C., “Introduction to Hardware-in-the-Loop Simulation”, Controllab Products B.V.
[4] Sarhadi P., Yousefpour S., “State of the art: hardware in the loop modelling and simulation with its applications in design, development and implementation of system and control software”, Springer-Verlag Berlin Heidelberg, 2014.
[5] LMS Amehelp, 2016.
[6] Bosch R., “Electronic Automotive Handbook”, 1st edition, 2002
[7] Velardocchia M., “Fondamenti su sistemi ABS”, lecture notes, a.y. 2016-2017, Corso di Laurea Magistrale in Ingegneria Meccanica, Politecnico di Torino.
[8] LMS Imagine.Lab Amesim™ User’s Guides, 2016.
[9] CarMaker® User’s Guide Version 6.0.
[10] CarMaker® Reference Manual Version 6.0.
154