Research on Speed ​​Control Characteristics and Vehicle Dynamics Improvement of Commercial Vehicle Electronic Control Diesel Engine

The speed control characteristic of the electronically controlled diesel engine is a control strategy that controls the engine operating state by using a specific algorithm in the engine speed region. The conventional speed regulation characteristic is the conventional input electronic throttle opening degree. The opening degree value reflects the driver's demand, and then is divided into ABT (two-pole speed regulation characteristic) and ABS (full-speed speed regulation characteristic) mode according to different internal algorithms of the software. A response to the torque output of the engine or a response to engine speed demand is achieved. On the basis of combining the above two characteristics of the regulator, the hybrid speed regulation characteristic can be generated. This paper combines the vehicle road test to optimize the speed regulation characteristics, and obtains the vehicle's dynamic performance based on the increase or decrease of the overall fuel consumption.

The throttle change of Cummins electronically controlled diesel engine can realize three different speed control modes: speed control, torque control and hybrid control: full-speed characteristic ABS, two-pole speed regulation ABT, and hybrid speed regulation.

The whole speed regulation characteristic takes the engine speed as the control target, the two-pole speed regulation characteristic takes the engine fuel injection amount (torque) as the control target, and the hybrid speed regulation characteristic is both, and both have the same control source - the throttle pedal.

The ABS calibrates the throttle pedal opening value to correspond to the engine speed, and controls the engine speed in the engine's adjustment control region. This control mode has a certain Droop (slope) and synchronous speed control, so that the requirements interaction, interface, initialization and performance requirements of the ABS full-speed speed regulation feature can be determined. ABS does not need to be particularly clear about control requirements. In short, the throttle opening corresponds to the engine speed, and the ABS speed characteristic is suitable for equipment that requires stable engine speed, and is often used in non-road equipment.

ABT is an engine control strategy based on controlling the accelerator pedal position opening to calibrate the engine output torque. According to the throttle position opening corresponding to the engine load standard, the speed of the engine is stabilized between the low idle speed and the maximum load speed, and the engine speed is related to the load condition. It is manifested that the engine speed decreases as the engine load increases. In order to increase the engine speed in the ABT mode, the torque demand should be increased to increase the opening. In short, the throttle pedal opening corresponds to the required torque. The ABT speed mode work state is smoother due to the change of engine speed, so it is superior in low load and road load equipment, and is often used in road vehicles.

The hybrid speed regulation feature is a mode that combines ABT and ABS with superior power. The ABT mode is aimed at smoothing the load change by the engine speed control; while the ABS mode is stabilized by the engine torque change control, so the ABT has the advantage that the driving operation is smooth, but the torque response is poor. The test proves that optimizing the calibration setting value of the hybrid speed regulation characteristic can greatly improve the dynamic performance on the basis of good driving characteristics and the comprehensive fuel consumption is not increased or slightly optimized.

This research object is Cummins 9L electronically controlled diesel engine, the engine output power is 290 ~ 375 horsepower (1 horsepower ≈ 0.735kW).

The speed regulation characteristics of ABT are shown in Figure 1. The calibration chart is analyzed as follows: The calibration torque at the 0% throttle is negative, and the purpose is to let the engine quickly return to idle when the valve is released. If the vehicle shifts gears when going uphill, the driver will feel that the engine speed drops faster and the power feels less. If the shifting mistake occurs again, the acceleration time of the engine in the low-speed maximum load region may be long or even stalled, and the driver feels that the power is insufficient.

At 100% throttle, the calibrated torque value is much larger than the external characteristic, and the purpose is to quickly respond to the engine when the throttle is added.

Figure 1 ABT speed regulation characteristics

The speed regulation characteristics of ABS are shown in Figure 2. The calibration chart is analyzed as follows: The reserve torque is large at 0% throttle opening, which makes the engine start load capacity strong. When the engine load changes greatly, the engine speed is stable. It still has a strong high load change capability in the high idle region of the 100% throttle.

When the whole speed regulation characteristic is applied to non-road vehicles, the engine speed stability is high and the load resistance change ability is strong. However, the fuel consumption rate is high. If it is applied to a road-driving vehicle, it is advantageous for the driver to shift gears during high-speed driving, but the comfort is not good, the vehicle is slightly worn on the road, and the vehicle has a perceptible tremor when the engine accelerates and decelerates.

Figure 2 ABS speed regulation characteristics

The speed regulation characteristics of the hybrid type 1 speed regulation characteristic (fixed slope type) are shown in Fig. 3. The calibration chart is analyzed as follows: This kind of speed regulation characteristic is a kind of speed regulation characteristic mode based on ABT and taking into account the advantages of two kinds of two-pole speed regulation characteristics and full-speed speed regulation characteristics, aiming at improving power and taking care of fuel consumption and comfort adjustment. A mode with better linearity for easy parameter distribution and integration.

Figure 3 hybrid type 1 speed regulation characteristics

The speed regulation characteristics of the hybrid type 2 speed regulation characteristic (variable slope type) are shown in Fig. 4. This kind of speed regulation characteristic is also a kind of speed regulation characteristic mode based on ABT and taking into consideration the advantages of two kinds of two-pole speed regulation characteristics and full-speed speed regulation characteristics. The purpose is also to improve the power, and take into consideration the fuel consumption rate and the comfort adjustment. Mode, but not with good linearity.

The advantage of the hybrid 2 speed regulation characteristic compared to the hybrid type 1 speed regulation characteristic is to realize the subdivision of the working condition area. When the power demand is large, that is, the low-speed region where the engine's conventional torque demand value is large, the variability is improved, and the high-speed region of the engine smoothly improves the comfort and reduces the fuel consumption rate. It has been proved by experiments that the improvement of dynamics is achieved under the premise of small changes in overall fuel consumption.

Figure 4 Hybrid 2 speed regulation characteristics

1. Test vehicle information

The test vehicle information is shown in Table 1.

Table 1 Test vehicle information

2. Vehicle test method

(1) Control conditions Vehicles, drivers, routes, and driving operations are consistent, with standard loads, sunny days less than three-level winds, and ambient temperatures of 10 °C to 16 °C.

(2) Data source The software used in engine development records data, real-time monitoring of operating conditions, and ensuring data accuracy.

(3) Adjust the ramp with the same physical position, the same gear, the same speed as the slope, full throttle control, shifting conditions operate in the same way.

(4) Dynamic analysis Analysis and comparison of vehicle gear status, shift status, engine speed change, integrated duration, fuel consumption and other data.

(5) Fuel consumption analysis Slope fuel consumption, record fuel consumption and mileage of road sections; comprehensive fuel consumption, statistics of oil consumption data and mileage throughout the day.

(6) Test section The slope of the high-speed ramp in the mountainous area is about 3.5%, and the slope of the national highway slope is about 6.5%.

3. Analysis of test data

(1) Analysis of shifting condition of high-speed ramp Under the condition of the same slope and the same driver, the highest gear enters the slope, the engine speed is reduced at 1200r/min, and the gear is increased at 1800r/min to monitor the speed and speed ratio. Bit), full throttle uphill. The ABT, ABS, Hybrid 1 and Hybrid 2 speed control characteristics were tested separately. The shifting condition of the ABT speed regulation characteristic is shown in Fig. 5. The shifting condition of the ABS speed regulation characteristic is shown in Fig. 6. The shifting condition of the hybrid type 1 speed regulation characteristic is shown in Fig. 7. The shifting condition of the hybrid type 2 speed regulation characteristic is shown in Fig. 8. According to Figure 5 and Figure 8, the analysis is as follows:

1) From the gear position, the hybrid 2 speed regulation characteristic (ABT2) is used, and the upper gear is completed with the 7th gear at the lowest speed of the incoming line, and the power is good.

2) From the low gear (6 gears) in the analysis of the gear duration, the full-speed governing characteristic (ABS) mode is relatively superior due to its larger slope, and the hybrid 1 governing characteristic (ABT1) is compared with the two-pole governing characteristic (ABT). Great advantage.

3) The comprehensive analysis concludes that the speed regulation characteristic has an influence on the dynamic performance, and the hybrid speed regulation characteristic has the function of improving the vehicle power.

Figure 5 Shift condition of ABT speed regulation characteristics

Figure 6 Shift condition of ABS speed regulation characteristics

Figure 7 Shift status of the hybrid 1 speed control feature

Figure 8 Shift status of hybrid 2 speed regulation

(2) Analysis of shifting conditions of national highway ramps Under the conditions of the same slope and the same driver, the speed of the incoming line is 50km/h. The addition and subtraction are determined by the driver according to the experience of use. The whole test is completed within four consecutive days. The ABT, ABS, Hybrid 1 and Hybrid 2 speed control characteristics were tested separately. The test results are shown in Table 2.

Table 2 National road ramp shift test results

The national road test conditions are complex and the number of shifts is high. This evaluation is based on the comprehensiveness of current data and operating conditions.

1) Analysis of low gear condition: The evaluation factors are the number of low gears and the total duration of low gears. The less comprehensive the better, the conclusion is that the hybrid 2 speed regulation characteristics are better than the full speed control characteristics ABS; the full speed control characteristics ABS It is superior to the hybrid 1 speed regulation characteristic; the hybrid 1 speed regulation characteristic is superior to the two-pole speed regulation characteristic ABT.

2) Analysis of high gear condition: The higher the gear position, the longer the time is, the better the comprehensiveness is. The analysis conclusion is that the hybrid 2 speed regulation characteristic is better than the full speed regulation characteristic ABS; the full speed regulation characteristic ABS is better than the hybrid type. 1 speed regulation characteristics; hybrid type 1 speed regulation characteristics are better than two-pole speed regulation characteristics ABT.

3) It is a hybrid type speed regulation characteristic with better improvement of power, which is beneficial to the driving shift of the national road slope, and the hybrid type 2 speed regulation characteristics are better.

(3) Comprehensive fuel consumption analysis of vehicles Under the same road section and the same driver's condition, the test vehicles were tested for fuel consumption rate in plain high-speed, mountainous high-speed and comprehensive road conditions, and each test was completed within 4 consecutive days. The ABT, ABS, Hybrid 1 and Hybrid 2 speed control characteristics were tested separately. The test results are shown in Figure 9. It can be seen that the hybrid fuel-speed characteristic has a superior fuel consumption rate.

Figure 9 Vehicle comprehensive fuel consumption test results

Through the above analysis, it can be seen that the hybrid speed regulation characteristic can improve the vehicle dynamics; the comprehensive fuel consumption rate of the hybrid speed regulation characteristic has an advantage; the whole speed regulation characteristic is not the most dynamic in the road transport vehicle.