CN101858813A - Calibration Method of Basic Inertia of Chassis Electric Dynamometer - Google Patents

Abstract

The invention belongs to the technical field of automobile detection, and relates to a method for calibrating the basic inertia of a chassis electric dynamometer. The method directly drives a drum through a motor, and makes the driving force of the motor only interact with the system inertia without adding any driving resistance Change the rotation speed of the drum, and in a fixed rotation speed range, apply a constant acceleration (or deceleration) to the drum to change the rotation speed evenly, and measure the basic inertia of the dynamometer based on the collected data. The invention can measure the actual size of the basic inertia of the dynamometer, calibrate the basic inertia of the dynamometer, improve the accuracy of the dynamometer, and reduce the error caused by the inertia in the automobile test.

Description

Calibration Method of Basic Inertia of Chassis Electric Dynamometer

technical field

The invention belongs to the technical field of automobile detection and relates to a method for calibrating the basic inertia of a chassis electric dynamometer.

Background technique

Chassis electric dynamometer is a special indoor vehicle testing equipment used in vehicle emission and durability tests, and can also be used in vehicle diagnosis and maintenance industries. It rolls with the driving wheel of the tested vehicle through the drum to simulate the driving state of the car on the road. By loading the inertia and resistance on the drum, it can simulate the driving state of the car on the road, and at the same time collect the driving speed, acceleration, driving force, etc. parameter. After the exhaust gas analyzer is installed, the emission performance parameters of the vehicle under specific working conditions can also be obtained by combining the loading resistance of different working condition curves. According to different types of vehicles, it is necessary to load different inertias on the drum during the test. The basic inertia is a unique parameter of the chassis electric dynamometer. It is the macroscopic system inertia formed by factors such as the rotational inertia of the dynamometer drum itself and the electrical inertia of the dynamometer system during the simulation of road loads. It is not included in the test loading inertia. among. Therefore, before determining the accuracy of the loading inertia, it is necessary to clarify the size of the basic inertia of the dynamometer system. In addition, the test results must also exclude the measurement error caused by the basic inertia.

Contents of the invention

The invention proposes a calibration method for the basic inertia of the electric dynamometer according to the structural characteristics and the performance characteristics of the basic inertia of the electric dynamometer of the chassis. After the accuracy and precision of the basic performances such as the speed, acceleration and driving force of the chassis dynamometer have been determined, the method of the present invention is used to carry out the no-vehicle loading test, and the results obtained by operating under different acceleration conditions are calculated. base inertia. For this reason, the present invention adopts following technical scheme.

A method for calibrating the basic inertia of a chassis electric dynamometer comprises the following steps:

(1) Isolate the dynamometer so that the motor directly drives the drum without any additional driving resistance;

(2) Start the electric dynamometer under the condition of no load, and set the inertia of the dynamometer as the basic inertia;

(3) Set the initial rotational speed, the highest drum speed and the measurement speed range between the two, and set the drum acceleration;

(4) Accelerate the drum to the initial rotational speed first, then accelerate to the highest rotational speed with a constant acceleration value, measure and record the time elapsed during the acceleration of the drum in the measurement speed range and the measured driving force; when the drum speed When the highest speed is reached, apply reverse driving force to decelerate the drum speed to the initial speed with a constant acceleration value, measure and record the time elapsed during the deceleration of the drum in the measurement speed range and the measured driving force;

(5) Repeat the measurement process of step (4) for more than 2 or 2 times, record the data records measured each time, and complete the measurement of the basic inertia once;

(6) Calculate the average value of the basic inertia values obtained by each measurement in each measurement speed interval, and use the average value as the average moment of inertia at the set acceleration place;

(7) Change the set drum acceleration, repeat steps (4) to (6) several times, obtain the average moment of inertia under each set acceleration, then calculate the average value for each average moment of inertia, and finally get The base moment of inertia of the dynamometer.

The invention can measure the actual size of the basic inertia of the dynamometer, calibrate the basic inertia of the dynamometer, improve the accuracy of the dynamometer, and reduce the error caused by the inertia in the automobile test.

Detailed ways

When the car is running on the road, the driving force overcomes the driving resistance to keep the car moving forward. In the test, the car body is fixed on the chassis electric dynamometer, and the driving wheel is in contact with the drum of the dynamometer and rotates at the same tangential linear velocity. State of motion on the road. The driving wheel of the car drives the drum to move, and at the same time drags the dynamometer motor coaxial with the drum, so that the motor generates power and feeds back to the grid, so as to detect the dynamic parameters of the tested car. Different from driving on real roads, the inertia loaded on the dynamometer includes not only the set inertia of the motor, but also the inertia generated by the drum and the dynamometer system. The sum of these inertias is expressed as a macro parameter: the basic inertia. The effect of the basic inertia will be considered during the test, so it is necessary to make an accurate calibration of this characteristic.

Since both the dynamometer and the car are complex systems, there are many factors that are difficult to determine, so each inertia appears in a macroscopic situation. Therefore, when determining the basic inertia, the test vehicle and the dynamometer are isolated, and the dynamometer is regarded as a separate measurement object. The drum is directly driven by the motor, and the driving force of the motor only interacts with the system inertia to change the drum speed without any additional driving resistance. In the fixed rotation speed range, by applying constant acceleration (or deceleration) to the drum to make it change the rotation speed evenly, according to Newton's law M=F/a, divide the motor drive F by the drum surface acceleration a, The equivalent inertia M of the system can be obtained - the basic inertia of the dynamometer. The measured result is taken as the final result by taking the average value of multiple measurements.

First install guardrails to prevent personnel from approaching the testing equipment. Connect the timer for measuring the rotation signal time (at present, many domestic and foreign products have built-in timing systems, which can no longer be installed) to the time output interface of the dynamometer system; connect the dynamometer motor driving force signal and the system acceleration measurement signal Connect to the chart recorder via a communication cable. Heat up the machine for 20 minutes (only for the dynamometer with the motor on the side, and the dynamometer with the motor in the middle does not need a heat-up), so that the drum shaft and the bearing are fully in contact with each other to make the drum measurement system sensitive and stable. Turn off road load and inertia simulation. In the speed mode of the dynamometer control software, set the measurement speed range to 16-64km/h and acceleration (such as 1kmph/s). Drive the drum at an initial speed of 8km/h, and then accelerate to a maximum speed of 72km/h at a fixed acceleration (1kmph/s). Measure and record the time elapsed for the drum to accelerate from 16km/h to 64km/h and the measured driving force in the timer. When the drum speed reaches 72km/h, apply a reverse driving force to decelerate the drum speed to 8km/h with a constant acceleration (such as 1kmph/s), measure and record the experience of the drum from 64km/h to 16km/h time and the measured driving force. Repeat the above measurement process four times continuously according to the set acceleration (1kmph/s), record the data measured each time in the data table, and complete a measurement of the basic inertia.

In this way, the basic inertia value Wi (i=1, 2, ... 9, 10) can be calculated in 5 measurement intervals with the set acceleration 1kmph/s as the acceleration:

${\mathrm{<span\; class="notranslate">\; W</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&Delta;V</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; \&Delta;t</span>}<span\; class="notranslate">\; )</span>}$

In the formula: Fi(i=1, 2, ..., 10) = driving force measured during acceleration; That is the acceleration a, where: V ₀ = drum surface velocity at the beginning of the sampling interval (16/64km/h); V ₁ = drum surface velocity at the end of the sampling interval (64/16km/h); t ₀ = sampling initial Time (when v=16/64km/h); t ₁ =sampling end time (when v=64/16km/h).

The average moment of inertia BIW1 of the drum under the acceleration of 1kmph/s is obtained by taking the average value of the basic inertia obtained in each acceleration interval:

${\mathrm{<span\; class="notranslate">\; BIW</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{\mathrm{<span\; class="notranslate">\; no</span>}}$

In the formula, n is the number of acceleration intervals, which is 10 here. Then set the acceleration as 2kmph/s, 3kmph/s, 4kmph/s, 5kmph/s respectively, measure the inertia value BIWj obtained under the corresponding acceleration with the same method above, and set the average value BIW of BIWj as the measured The final base inertia in the power machine control software.

$\mathrm{<span\; class="notranslate">\; BIW</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; BIW</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}}{\mathrm{<span\; class="notranslate">\; m</span>}}$

In the formula: BIWj (j=1, 2, . . . , 5) = the inertia value obtained under each acceleration; m = the number of set accelerations, which is 5 here.

Claims (1)

1. A method for calibrating the basic inertia of a chassis electric dynamometer, comprising the following steps: (1) Isolate the dynamometer so that the motor directly drives the drum without any additional driving resistance; (2) Start the electric dynamometer under the condition of no load, and set the inertia of the dynamometer as the basic inertia; (3) Set the initial rotational speed, the highest drum speed and the measurement speed range between the two, and set the drum acceleration; (4) Accelerate the drum to the initial rotational speed first, then accelerate to the highest rotational speed with a constant acceleration value, measure and record the time elapsed during the acceleration of the drum in the measurement speed range and the measured driving force; when the drum speed When the highest speed is reached, apply reverse driving force to decelerate the drum speed to the initial speed with a constant acceleration value, measure and record the time elapsed during the deceleration of the drum in the measurement speed range and the measured driving force; (5) Repeat the measurement process of step (4) for more than 2 or 2 times, record the data records measured each time, and complete the measurement of the basic inertia once; (6) Calculate the average value of the basic inertia values obtained by each measurement in each measurement speed interval, and use the average value as the average moment of inertia at the set acceleration place; (7) Change the set drum acceleration, repeat steps (4) to (6) several times, obtain the average moment of inertia under each set acceleration, then calculate the average value for each average moment of inertia, and finally get The base moment of inertia of the dynamometer.