Introductions of semi-trailers ABS system (Part 3)

Introductions of semi-trailers ABS system (Part 3)

-Common semi trailer ABS arrangement modes

1. Composition of semi-trailer ABS system

The main components of semi-trailer ABS include: wheel speed sensors, which record the speed of wheels; the brake pressure regulators, which adjust the pressure of the wheel brake cylinder when ABS works; electronic control unit (ECU), which is the core component of ABS, is composed of high-performance single-chip microcomputer and integrated circuit, embedded with optimized high-level language algorithm and logic. It controls the pressure control valve according to the signal processing of wheel speed sensor, and then controls the braking torque of corresponding wheels, and finally completes the control function of vehicle anti-lock braking.

As shown in Figure 1 below, the 4S2M ABS system is installed on the 2-axle semi trailer, that is, 4 wheel speed sensors and 2 pressure control valves (ABS solenoid valves). S: the number of wheel speed sensors, M: the number of regulators.

(1. Speed sensor 2. Electronic control unit(ECU) 3. Pressure regulator 4. Brake chamber 5. Air tank 6. Relay valve 7. one-way valve 8. Flexible joint of air source 9.Control joint of air source)

Figure 1. 2-axle semi-trailer with 4S2M arrangement mode

2.Common ABS arrangement modes

(1) 2S1M arrangement mode

As shown in Figure 2 below, 2S1M mode is the basic semi-trailer ABS system. The whole system is equipped with 1 regulating valve and 2 speed sensors, and the brake pressure of all wheels is equal. Since 1 solenoid valve needs to supply compressed air to all brake chambers, in order to ensure the braking response time of the semi-trailer, this arrangement mode is recommended to be used on the semi-trailer with two axles or less.

For single-axle semi-trailers, wheel speed sensors are installed on both wheels, and the MAR control mode is adopted.

For 2-axle semi-trailers, there is 1 wheel speed sensor on each side, which can be installed on the front or rear axle, or can be arranged diagonally (this mode is not often used), and the MAR and INSR control modes are adopted. This mode regulator is different from the single-axle mode regulator. It has 4 air outlets, which are distributed to 4 chambers.

For 3-axle semi-trailers, 2 wheel speed sensors are usually installed on the front axle or intermediate axle, using MAR and INSR control modes. This mode regulator has 6 air outlets, which are distributed to each chamber respectively.

Figure 2. 2S1M arrangement mode

(2) 2S2M arrangement mode

As shown in Figure 3 below, 2S2M mode is equipped with 2 regulators and 2 speed sensors, which are mainly used for 2-axle and 3-axle semi trailers. Generally, its performance is close to that of 2S1M.

For 2-axle semi-trailers, 2 wheel speed sensors can be installed on the front axle or the rear axle, using MSR and INSR control modes.

For 3-axle semi-trailers, 2 wheel speed sensors are usually installed on the intermediate axle and adopt MSR and INSR control modes. Depending on the function and style of the regulator, 2 or 3 wheels on one side can be controlled respectively. This mode is applicable to both air suspension and leaf spring suspension.

Figure 3.2S2M arrangement mode

(3) 4S2M arrangement mode

As shown in Figure 4 below, the 4S2M mode is equipped with 4 wheel speed sensors and 2 regulators, which are mainly used for 2-axle and 3-axle semi trailers or full trailers.

For 2-axle semi-trailers, each wheel is equipped with a wheel speed sensor, which can ensure that each wheel is not locked and obtain better braking performance. There are two control modes: 1) Modified Side Regulate (MSR) control mode; 2) Modified Axle Regulate (MAR) and Variable Axle Regulate (VAR) control modes;

For 3-axle semi trailers, 4 wheel speed sensors are usually installed on the first and third axles. There are two control modes: 1) Modified Side Regulate (MSR) and Indirect Side Regulate (INSR) control modes; 2) Modified Axle Regulate (MAR), Variable Axle Regulate (VAR) and Indirect Axle Regulate (INAR) control modes.

Figure 4. 4S2M arrangement mode

(4) 4S2M arrangement mode

As shown in Figure 5 below, the 4S3M system is equipped with 4 wheel speed sensors and 3 regulators, which are mainly used for 2-axle and 3-axle full trailers or semi trailers.

For 2-axle semi-trailers, each wheel is equipped with a wheel speed sensor, which can ensure that each wheel is not locked and obtain better braking performance. It adopts the control mode of front axle Individual Regulate (IR) and rear axle Variable Axle Regulate (VAR).

For 3-axle semi-trailers, only 4 wheels are equipped with wheel speed sensors, and the front and rear axles are usually selected to be installed wheel speed sensors. The front axle adopts Modified Side Regulate (MSR), Indirect Axle Regulate (INSR) and rear axle Modified Axle Regulate (MAR) control modes.

For 2-axle full trailers, each wheel is equipped with a wheel speed sensor, which can ensure that each wheel is not locked. The front axle adopts the Modified Axle Regulate (MAR) and the rear axle adopts the Individual Regulate (IR) control mode.

For 3-axle full trailers, only 4 wheels are equipped with wheel speed sensors. Usually, the front axle and the middle axle are selected to be installed wheel speed sensors. The front axle adopts the control mode of Modified Axle Regulate (MAR), the middle axle adopts the control mode of Modified Side Regulate (MSR), and the rear axle adopts the control mode of Indirect Side Regulate (INSR).

Figure 5. 4S3M arrangement mode

(5) 4S4M arrangement mode

As shown in Figure 6 below, the 4S4M system is equipped with 4 wheel speed sensors and 4 regulators, which are mainly used for 2-axle and 3-axle full trailers or semi trailers.

For 2-axle semi-trailers, there are wheel speed sensors on 4 wheels, each sensor corresponds to a regulator, and the Individual Regulate (IR) control mode is adopted.

For 3-axle semi-trailers, only 4 wheels are equipped with wheel speed sensors. Generally, the first axle and any rear axle are selected to be installed wheel speed sensors. It adopts the control modes of Individual Regulate (IR), Modified Side Regulate (MSR) and Indirect Side Regulate (INSR).

For 2-axle full trailers, there are wheel speed sensors on 4 wheels, each sensor corresponds to a regulator, and the Individual Regulate (IR) control mode is adopted.

For 3-axle full trailers, only 4 wheels are equipped with wheel speed sensors. Usually, the front axle and any rear axle are selected to be installed wheel speed sensors. It adopts the control modes of Individual Regulate (IR), Modified Side Regulate (MSR) and Indirect Side Regulate (INSR).

Figure 6. 4S4M arrangement mode

(6) 6S3M arrangement mode

As shown in Figure 7 below, 6S3M system is equipped with 6 wheel speed sensors and 3 regulators, which are mainly used for 3-axle semi-trailers or full trailers.

For 3-axle semi-trailers, wheel speed sensors are installed on 6 wheels, and there are two control modes: 1) Modified Side Regulate (MSR) and Individual Regulate (IR). The first or third axle can be selected for independent control. 2) Modified Axle Regulate (MAR) is selected for all three axles.

For 3-axle semi-trailers, wheel speed sensors are installed on 6 wheels, and there are two control modes: 1) front axle Individual Regulate (IR) control mode and rear axle Modified Side Regulate(MSR). 2) Modified Axle Regulate (MAR) is selected for all three axles.

Figure 7. 6S3M arrangement mode

(7) 6S3M arrangement mode

As shown in Figure 8 below, 6S6M system is equipped with 6 wheel speed sensors and 6 regulators, which are mainly used for 3-axle semi-trailers or full trailers.

For 3-axle semi-trailers or a full trailers, there are wheel speed sensors on 6 wheels, each sensor corresponds to a regulator, which has a very good anti-lock effect. The Individual Regulate (IR) control mode is adopted.

Figure 8. 6S6M arrangement mode

3. Selection of ABS arrangements modes

For a 2-axle semi-trailer, 4S/4M is the most sufficient system allowed to be arranged, that is, 2 wheel speed sensors and 2 regulators; for a 3-axle semi-trailer, 6S6M is the most adequate system allowed.

It is generally believed that the folding of a semi-trailer is caused by the fact that it is difficult to generate a lateral force between the rear axle tires of the semi-trailer and the road surface, which is sufficient to maintain the stable operation of the semi-trailer, leading to the side slip of the rear wheel, resulting in the folding. This kind of folding often occurs when the semi-trailer brakes on a curve on a slippery road or turns suddenly. Therefore, in order to avoid folding, for semi-trailers, try to avoid using IR control mode, and it is recommended to use MIR control mode.

In view of the frequent sideslip of trailer tires on slippery roads, which directly leads to the tail flick of semi-trailers, it is recommended to adopt the 4S2M arrangement for 2-axle semi-trailer, and apply the Modified Side Regulate (MSR). In this way, the wheels of the semi-trailer will not be locked, so that the wheels can obtain the maximum lateral force and avoid tail flicking as much as possible.

The manufacturer can select a reasonable ABS arrangement mode and control mode according to the different uses of the vehicle and refer to the above introduction, considering the instability of the semi-trailer such as folding and tail flicking.

Compiled by  WONDEE Autoparts

2022-6-6