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Design and manufacture of electric power steering system model - 9


The output has continuous changes, making the signals susceptible to noise when operating, so it is necessary to build a voltage loop circuit to avoid noise before sending the signal to the pic.

Just like the sensor presented, the circuit will receive signals such as: 3.9 and 1.1 V when rotating left, rotating right and in the middle position is 2.5 V


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Figure 4.9 Signal voltage loop circuit

Signal display circuit.

The display circuit is designed to help recognize the signal or the different levels of change between the signals of the digital signal circuits. And show the direction of rotation of the steering wheel, when we turn left or right,



Figure 4.10 Signal display circuit




Figure 4.11 Printed circuit board displaying signal


Figure 4.12 Actual display circuit

In particular, the circuit uses 7-segment LEDs to display and ICs such as: 74LS138, 74LS47, used to latch and filter signals to display numbers in the most optimal way, saving pins for LEDs when inserted into the pic.

Almost all control circuits have a reset circuit or reset button, when pressed it allows the circuit to start over from the beginning, meaning the input signals or output signals are displayed again from the beginning.


Figure 4.13 Reset circuit

Power circuit.


Electric power steering system using DC motor is quite popular in Vietnam market now, but to design a motor control circuit to operate, not only must 12V voltage be supplied but the current must also be calculated to match the motor.

Suzuki uses a motor with a relatively large current to activate the servo motor through the intermediate screw-worm gear mechanism. To achieve that, it is necessary to calculate and design a power circuit with 4 mosfets to set up an H-bridge circuit that can respond to a current of about 10A-40A.



Figure 4.14 Power circuit



Figure 4.15 Actual power circuit

Power circuit.

The power circuit is an indispensable part of any control circuit. The reason for manufacturing the power circuit is because: Components on the Vietnamese market always have different power supplies and depending on the circuit design for different devices, leading to different power supplies. However, to overcome that, the model is designed for each circuit cluster in the control circuit. There are many types of booster and step-down circuit designs, using ICs such as: LM7805, LM7809, or LM7905, LM7909. Here, the model uses IC LM7805 to reduce voltage from 12V-5V.


Figure 4.16 5V power circuit


Connection port

A connector is used to connect pins from the circuit to the outside of the circuit and vice versa from the outside to the inside of the circuit through the connector pins. Here the model is illustrated for a 4-pin port that receives signal current from the outside into the circuit.


Figure 4.17 Connection port


Control circuit diagram


Figure 4.18 Control circuit



Figure 4.19 Actual control circuit.


With the diagrams: Turn, Light and Interrupt will illustrate the control process from start to finish, will help readers have a more general view of the system.

General flow chart of the model: Legend:

- The blue line shows the motor control signal.

- Black line shows LED signal. Shows signal does not rotate motor.

- The yellow line shows the cycle of the operating cycle.

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