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Introductions of semi-trailers ABS system (Part 2)

Views: 0     Author: Wondee Autoparts     Publish Time: 2022-05-30      Origin: Wondee Autoparts

Introductions of semi-trailers ABS system (Part 2)

-working principle, working parameters and arrangement modes


1. Working principle of ABS system


Semi-trailer ABS(Anti-lock Braking System)is a kind of mechatronics system, which can prevent the wheels from being locked when the vehicle is in emergency braking, make full use of the longitudinal and transverse friction coefficient between the tire and the ground, and control the wheel slip rate within a reasonable range, so as to obtain a shorter braking distance and better controllability of the vehicle, so as to avoid traffic accidents and reduce the damage caused by traffic accidents as much as possible.

The working principle of the ABS system is shown in Figure 1 below. Firstly, the Speed Sensor (1) and the Gear Ring (2) work together to generate an induced voltage signal, which is transmitted to the Electronic Control Unit(ECU) (3); the ECU (3) receives and processes the voltage signal from the Speed Sensor (1) and sends the signal to the Regulator (4); the Regulator (4) adjusts the braking pressure of the Brake Chamber according to the command sent by the ECU (3), realizes the control of the braking force, and the ABS system finally realizes the control of the vehicle braking slip rate.


Working principle of ABS system

Figure 1. Working principle of ABS system


2. Working parameters of ABS system


The working parameters of vehicle ABS are shown in Table 1 below.

 Models Parameter

 2S/1M  2S/2M    4S/2M  4S/3M  4S/4M      6S/3M  6S/6M

Working voltage

    24-2.4+4.8V

Working temperature

    -40℃~80℃

Working medium

  Air

Working pressure

    8bar

Maximum allowable pressure

    10bar

Table 1. ABS system working parameters

3. Arrangement modes of ABS system

ABS system is applicable to various types of semi trailer, and different semi trailer models have a variety of arrangement modes.

The following factors shall be comprehensively considered in the arrangements of semi-trailer ABS system:


1) Control modes of ABS

Semi-trailer ABS mainly has the following control modes:


① IR:(Individually Regulate)

Each wheel has its own independent speed sensor and brake pressure regulator. ECU can control the wheel braking according to the actual situation of each wheel.

Advantage: 

from the perspective of controlling the anti lock braking pressure of wheels, the separate control of each wheel is a more optimized control mode.

Shortage:  

when the left and right wheels are on different road conditions (wet/dry), due to the large difference in the adhesion coefficient between the left and right wheels, this control mode will reduce the handling stability of the vehicle.


② MIR:Modified Individually Regulate)

Advantages: 

1) Reduce the swing movement of the vehicle when ABS starts to work and improve driving stability;

2) The adjustment angle of the steering angle is relatively moderate.


③ MAR:(Modified Axle Regulate)

Left and right wheels of a semi-trailer axle will be controlled by one regulator at the same time. There is a sensor on each wheel. The two sensors provide signals to  ECU at the same time. The ECU outputs the control signal to the regulator on the axle according to the low selection principle. Two wheels’ braking of the axle will be controlled by the regulator at the same time.  As a result, both wheels are controlled without locking.

Advantages: 

1) the swing movement of the vehicle is less;

2) When the left and right wheels are on different roads (wet / dry), the adjustment angle of steering angle is relatively small.

Shortage: 

compared with MIRModified Individually Regulatecontrol mode, the braking distance is longer.


④MSR:(Modified Side Regulate)

Two wheels on the same side of two axles will be controlled by one regulator at the same time. There is a sensor on each wheel. The two sensors provide signals to the ECU at the same time. The ECU outputs the control signal to the regulator on the same side according to the low selection principle. Two wheels’ braking on the same side will be controlled by the regulator at the same time. As a result, both wheels are controlled without locking. The brake control of the two wheels on the other side is the same.


⑤VAR:(Variable Axle Regulate)

Two wheels on one axle will be controlled by one regulator at the same time.

There is a sensor on each wheel. The two sensors provide signals to ECU at the same time. ECU outputs the control signal to the regulator on the axle according to the high selection principle. The braking of two wheels of the axle will be controlled by the regulator at the same time.

When the left and right wheels are on different roads (wet / dry), the wheel with low adhesion coefficient are allowed to lock.


Advantages: 

1) The braking distance is almost the same as the MIRModified Individually Regulatecontrol mode; 2) Moderate steering angle.


Working process: when the wheels are on the road with the same adhesion coefficient, the working process is similar to MARModified Axle Regulate. When the left and right wheels are on different roads (wet / dry), this control mode allows the wheel on the road with low adhesion coefficient to be locked temporarily, so that the wheel on the road with high adhesion coefficient have greater braking pressure, so as to shorten the braking distance. The maximum cycle braking pressure of ABS depends on the reaction of wheel on the road with low coefficient of adhesion, the number of cycles, speed and the reaction of rear wheels.

The parameter setting of this control mode needs to be set according to the vehicle model and verified by experiments.


⑥INSR:(Indirect Side Regulate )

Generally, the rear axle without sensor can adopt this control mode. The sensorless rear axle is controlled by the regulator of another rear axle with sensor to control the wheels on the same side.


The wheel brake pressures on the left and right sides of this control mode are independent. The brake pressure on each side is controlled according to the signal of a speed sensor.


⑦ INAR: (Indirect Axle Regulate)

Generally, the rear axle without sensor can adopt this control mode. The sensorless rear axle is controlled by the regulator of another rear axle with sensor to control the left and right wheels on the same axle.

2) Number of sensors

3) Number of regulators


4) Number of controlled axles


5) Number of axles of trailers

Theoretically, only when each brake chamber is equipped with a set of sensors and regulators, the friction between the ground and the wheels can be full used. However, in the mature market, the performance and price of trailer ABS are matched based on the consideration of cost, and the configuration of semi-trailer ABS is standardized.

At present, there are mainly ABS systems with the following configurations in the market, as shown in Table 2 below.

Category

2S/1M

2S/2M

4S/2M

4S/3M

4S/4m

6S/3m

6S/4M

6S/6m

 Number of   sensors

2

2

4

4

4

6

6

6

Number of regulators

1

2

2

3

4

3

4

6

Control principle

MAR

IR

MSR

MAR/

MSR

IR

MAR/

MSR

MAR/

MSR

IR

 Number of controlled axles

1

1

2

2

2

3

3

3

Applicable trailer type (number of   trailer axles)

1、2、3

2、3

2、3

2、3

2、3

2、3

2、3

2、3

Table 2. ABS system configuration table

Explanation:

2S / 1M, ---2 sensors, 1 regulator

2S / 2M, ---2 sensors, 2 regulators

4S / 2M, ---4 sensors, 2 regulators

......

6S / 6M, ---6 sensors, 6 regulators


4. Common ABS system arrangements modes

After the connection of semi-trailer and tractor, the semi-trailer usually has an elevation angle. For the semi-trailer with multi axle leaf spring suspensions, this will inevitably lead to different axle loads of each axle. That is to say, the braking locking pressure of the wheels on the same side is inconsistent, and semi trailer ABS usually has a regulator that controls several wheels, so the semi-trailer ABS system cannot transmit the optimal braking force to each wheel. Through reasonable sensor arrangement, better braking effect can be obtained.

The ABS system of semi-trailer has the following common arrangements:


1) The installation diagram of 2S / 1M on 2-axle trailer (MAR, INSR control modes) is shown in Figure 2 below:

2S - 1M on 2-axle trailer

(1. Gear ring 2. Regulator 3. ECU 4. Brake chamber 5. 7-core cable connector 6. Diagnostic interface)

Figure 2.The installation diagram (MAR, INSR control modes) of 2S / 1M on 2-axle trailer

2) The installation diagram (MSR control mode) of 2S / 2M on 2-axle trailer is shown in Figure 3 below:

2S - 2M on 2-axle trailer

(1. Gear ring 2. Regulator 3. ECU 4. Brake chamber 5. 7-core cable connector 6. Diagnostic interface)

Figure 3.The installation diagram (MSR control mode) of 2S / 2M on 2-axle trailer


3) The installation diagram (MSR control mode) of 4S / 2M on 2-axle trailer is shown in Figure 4 below:

4S - 2M on 2-axle trailer

(1. Gear ring 2. Regulator 3. ECU 4. Brake chamber 5. 7-core cable connector 6. Diagnostic interface)

Figure 4.The installation diagram (MSR control mode) of 4S / 2M on 2-axle trailer

Compiled by  WONDEE Autoparts

2022-5-30

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