CN110646224B - Method for measuring instantaneous output power of vehicle drive wheels - Google Patents
Method for measuring instantaneous output power of vehicle drive wheels Download PDFInfo
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Abstract
本发明提供一种车辆驱动轮瞬间输出功率的测量方法，S1、制作通用型的可调节轴距的挂车来模拟不同车型及其的重心位置；S2、运用底盘测功机反拖与被车测量等质量且等重心位置的挂车至车速达到达到，其中大于待测速度，通过底盘测功机将挂车行驶时的动能储存下来，采集测功机滚筒的转速以及该转速度时刻的转角加速度，结束第一次反拖挂车的滑行实验；S3、进行第二次滑行计算出时刻车轮与滚筒之间的滚动摩擦阻力矩与测功机传动系统阻力矩之和；S4、测量车辆驱动轮瞬间输出功率。本发明为车辆驱动轮输出功率的精确免拆快速检测以及测功机精确模拟车辆道路行驶阻力提供了更为精准的数据。
The present invention provides a method for measuring the instantaneous output power of a vehicle driving wheel. S1. Making a universal trailer with adjustable wheelbase to simulate different vehicle models and the position of their center of gravity; S2. Using a chassis dynamometer to reverse drag and measure the vehicle When the trailer with equal mass and equal center of gravity reaches the vehicle speed, which is greater than the speed to be measured, the kinetic energy of the trailer when driving is stored by the chassis dynamometer, and the rotational speed of the dynamometer drum and the angular acceleration at the time of the rotational speed are collected, and the end The first sliding experiment of the anti-trailer; S3. Calculate the sum of the rolling friction resistance torque between the wheel and the drum and the resistance torque of the dynamometer transmission system for the second sliding; S4. Measure the instantaneous output power of the vehicle driving wheel . The present invention provides more accurate data for accurate dismantling-free and rapid detection of the output power of the vehicle driving wheel and for the dynamometer to accurately simulate the road running resistance of the vehicle.
Description
Technical Field
The invention belongs to the field of vehicle driving wheel instantaneous output power measurement, and particularly relates to a method for measuring vehicle driving wheel instantaneous output power.
Background
The traditional vehicle driving performance test is to establish a road driving resistance model for analysis and research through a road driving test, and the detection process is complicated due to the influence of external environment factors such as air pressure, temperature, humidity and the like. The chassis dynamometer is a test platform for the comprehensive performance of the whole vehicle, and is widely applied to the aspects of the dynamic property, braking property, economic fuel property, emission property and the like of the whole vehicle. The chassis dynamometer mainly comprises a roller, a simulated resistance loading device, a rotating speed and torque measuring device and a control and display device. In the process of testing the dynamic performance of the vehicle, the output power of the driving wheel is an important index for measuring the dynamic performance of the vehicle. The traditional method for testing the output power of the driving wheel of the vehicle by using the chassis dynamometer is that the driving wheel of the vehicle is arranged on a roller, after the vehicle is started, the output torque of an engine passes through a vehicle transmission system and then reaches the driving wheel, the driving wheel drives the roller of the dynamometer to rotate and a transmission device of the dynamometer to rotate, eddy current generated by a dynamometer motor generates braking torque opposite to the driving torque on a rotor of the dynamometer, the braking torque is equal to the driving torque of the roller of the driving wheel, the driving torque of the roller of the driving wheel is obtained by detecting the electromagnetic torque of the driving wheel, and the braking torque is multiplied by the rotating speed of the roller to obtain the output power of the driving wheel.
In the measuring method, because the friction loss between the vehicle tire and the roller of the dynamometer and the friction loss of the transmission system of the dynamometer exist, the measured power does not include the rolling resistance loss power consumption between the driving wheel and the roller and the friction power consumption in the dynamometer on the roller chassis in the testing process, and the power value displayed by the dynamometer cannot truly reflect the magnitude of the vehicle driving power. Aiming at the problem that the power value displayed by the dynamometer of the roller chassis dynamometer cannot truly reflect the magnitude of the driving power of the automobile, a plurality of scholars carry out related research. Irimescu, l.mihon and G.
Automotive Transmission efficiency measurement using a chassis dynamometer[J]International Journal of Automotive Technology, 2011,12(4): 555-. Zhao Renwei, Wangqiang, Jingqi feng, Wanglin, research on wheel instantaneous power measurement method based on AT89S52 [ J]The 73-76 of 73-76 provides a new method for measuring the instantaneous power of wheels of the engineering machinery, the rotating speed, the torque and the angular acceleration of the roller are measured, the influence of moment unbalance on the measurement precision is reduced, the limitation that the measurement is only carried out in the relative balanced state of the roller and the wheels in the prior art is overcome, and the accuracy of the measurement of parameters such as the power under the unbalanced condition is improved. Mathematical model [ J ] for indoor accurate detection of vehicle driving wheel output power]Mechanical design and study 2017, 33 (8): 146-The self-loss power of the chassis dynamometer is measured, then the secondary loading sliding method is adopted to reversely drag the vehicle, a mathematical model of the frictional resistance between the roller of the roller chassis dynamometer and the automobile driving wheel is established, and a theoretical basis is established for the actual condition that the detected value of the chassis dynamometer can more accurately reflect the dynamic performance of the vehicle. Research on experimental error analysis and method of dynamic performance of chassis of engineering machinery based on dynamometer [ J]China test, 2019,45(5): 151-. Mathematical model research on frictional resistance between roller of chassis dynamometer and automobile driving wheel [ J]2017,8(8):1-5, provides a method for measuring relevant data of a vehicle sliding on a chassis dynamometer by adopting a no-loading sliding method and a secondary loading sliding method respectively, establishes a mathematical model of the output power of an automobile driving wheel based on a single-roller chassis dynamometer by adopting an energy conservation law, and lays a theoretical foundation for accurate disassembly-free rapid detection of the output power of the automobile.
In a loading sliding test experiment, the self friction resistance torque of the dynamometer and the rolling resistance torque of wheels and a roller change along with the change of the speed of the roller, so that secondary loading sliding and non-loading sliding are a variable acceleration motion process, the acceleration gradually decreases along with the rotating speed of the roller, the resistance torque is regarded as constant torque in the traditional test process, and the variable acceleration process is regarded as a uniform speed change process in a certain speed interval; in the process of testing the rotational inertia of the transmission system of the dynamometer by adopting a method of towing a vehicle reversely, the measured rotational inertia value comprises the rotational inertia equivalent to a roller of the dynamometer of the vehicle transmission system, so that the precision of a mathematical model of the output power of the driving wheel is reduced; in the process of measuring the output power of the driving wheel, the vehicle is in a balanced state by the traditional test method, and the influence of the moment of inertia caused by the angular acceleration of the roller on the output power test of the driving wheel is ignored.
Disclosure of Invention
The invention aims to provide a method for measuring the instantaneous output power of a vehicle driving wheel, which can accurately and quickly detect the output power of the vehicle driving wheel without disassembly.
The invention provides the following technical scheme:
a method for measuring the instantaneous output power of a vehicle driving wheel comprises the following steps:
s1, manufacturing trailers capable of simulating different vehicle types and gravity center positions of the vehicles;
s2, carrying out a first sliding experiment, and acquiring the rotating speed omega of the roller of the dynamometer0＝v0/r and angular acceleration a of the rotation at the time of the rotation speed1；
S3, carrying out a second sliding experiment, and acquiring the rotating speed omega of the roller of the dynamometer0＝v0/r and angular acceleration a of the rotation at the time of the rotation speed2While simultaneously calculating omega0The sum of the rolling friction resisting moment between the wheel and the roller and the resisting moment of the dynamometer transmission system at the moment;
and S4, measuring the instantaneous output power of the driving wheels of the vehicle.
Further, S1, manufacturing a general trailer with an adjustable wheelbase, carrying weights with different masses on the trailer to meet the requirements of different vehicle types, and simultaneously adjusting the positions of the weights to simulate the gravity center positions of different vehicle types;
further, S2, using the chassis dynamometer to reversely drag the trailer with equal mass and equal gravity center position as measured by the trailer until the vehicle speed reaches v, wherein v is greater than the speed v to be measured0Storing the kinetic energy of the trailer during running through a chassis dynamometer, and then loading a resistance torque T to the experimental trailer1Trailer at drag torque T1Rolling friction resistance torque T between roller and wheelfcAnd dynamometer drive system moment of resistance TrcSlide under the combined action of the two components to acquire the rotating speed omega of the roller of the dynamometer0＝v0/r and angular acceleration a at the time of the rotational speed1Ending the first sliding experiment of the trailer;
further, S3, performing second sliding, and performing second sliding by using a chassis dynamometerThe test vehicle being loaded with a load other than T1Loading resisting moment T2Collecting the rotation speed omega of the dynamometer roller0＝v0/r and angular acceleration a at the time of the rotational speed2And establishing a mathematical model by using the theorem of angular momentum:
in the formula, alpha1Angular speed ω of the cylinder during the first load sliding0Angular acceleration of time, α2Angular speed ω of the cylinder during the second loading stroke0The angular acceleration of (a). The equivalent rotary inertia J of the dynamometer transmission system to the roller is shown as formula (2), and omega is calculated simultaneously0The sum T of the rolling friction moment between the wheel and the roller and the moment of resistance of the transmission system of the dynamometer at the momentfc+TrcAs shown in formula (3),
further, S4, the measurement of the instantaneous output power of the driving wheel of the vehicle, can be performed according to equation (4)
PP＝(Tfc+Trc+Tl+Jα)·ω (4)
The formula (2) for obtaining the instantaneous output power and output torque of the vehicle driving wheel is shown as the formula (5)
In the formula, TsThe torque value is recorded by the sensor, and the torque value is loaded to the dynamometer and the rolling friction torque T between the roller and the wheelfcAnd dynamometer drive system moment of resistance TrcSum of。
Further, the method for obtaining formula (4) in S4 is as follows:
the output power of a vehicle driving wheel at any moment is measured under the working condition of variable-speed running of the vehicle, the driving torque and the roller resistance torque of a roller of a dynamometer are unbalanced due to the fact that the wheel and the roller have certain angular acceleration, and the system reaches a balanced state after adding a reverse inertia torque according to the Dalnobel principle, and at the moment, a torque equation is as follows:
TD-(Trc+Tl)＝TP-(Tfc+Trc+Tl)＝Jα (6)
wherein J is the rotational inertia equivalent to the roller of the chassis dynamometer transmission system, alpha is the angular acceleration of the dynamometer roller, J alpha is the inertia moment, the driving force power output to the roller by the vehicle driving wheel is expressed by the formula (4),
PP＝(Tfc+Trc+Tl+Jα)·ω (4)。
the invention has the beneficial effects that: establishing a mathematical model of the instantaneous power test of a driving wheel in the variable-speed running process of the vehicle by analyzing the moment borne by a roller in the variable-speed running process of the vehicle on a dynamometer; considering friction loss in the dynamometer and rolling loss of wheels and rollers, testing state variables such as roller rotating speed, torque, angular acceleration and the like through a sensor arranged on a roller connecting shaft of the dynamometer; in the secondary loading sliding process, a method of reversely dragging a trailer with the same mass as the tested vehicle is adopted, the friction resistance moment inside the dynamometer and the rolling resistance moment between the vehicle and a roller are measured, and the equivalent rotary inertia of the dynamometer is tested; on the basis, the method for measuring the instantaneous power of the vehicle driving wheel based on the vehicle variable-speed running working condition is provided, the instantaneous output power of the vehicle driving wheel is obtained through calculation of a mathematical model, the output power of the vehicle driving wheel can be accurately and quickly detected without disassembly, and a theoretical basis is provided for a dynamometer to accurately simulate the road running resistance of the vehicle.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:
FIG. 1 is a diagram of dynamometer machine roller force analysis in equilibrium;
FIG. 2 is a diagram of dynamometer machine roller stress analysis in a non-equilibrium state;
FIG. 3 is a schematic diagram of the working principle of the magnetoelectric rotation speed torque sensor, wherein 1 magnetic steel, 2 coils, 3 signal gears and 4 elastic shafts are arranged;
FIG. 4 is a schematic view of a chassis dynamometer system;
FIG. 5 is a schematic diagram of a signal acquisition processing system;
FIG. 6 is a graph of drive wheel output torque at different vehicle speeds;
FIG. 7 is a diagram of relative error of a driving wheel output power calculation model.
Detailed Description
As shown in fig. 1-7, the influence factors of the output power of the driving wheels of the vehicle are analyzed:
the output power of the vehicle engine can be expressed as
Pt＝Pr+Pf+Pw+Pi+Pj (21)
In the formula: pt-vehicle engine output power; pr-vehicle driveline resistive power loss; pfVehicle drive wheel rolling resistance loss power; pw-vehicle driving air resistance power loss; pi-slope drag loss power; pj-acceleration resistive loss power.
When the vehicle is subjected to a dynamic performance test on an indoor dynamometer test platform, in order to simulate the acceleration resistance, the air resistance, the gradient resistance and the like which are applied to the road surface running of the vehicle, a dynamometer motor is used as a loading resistance device to simulate the real running condition of the vehicle. The vehicle engine output power may be expressed as the vehicle engine output power during a test on a chassis dynamometer drum
Pt＝Pr+Pfc+Prc+Ps (22)
In the formula: pfc-vehicle tyre and dynamometer machine roller rolling resistance power loss; prc-the self power loss of the chassis dynamometer; psThe dynamometer absorbs power.
Changing formula (1) to Pt-Pr＝Pfc+Prc+PsTo obtain
PP＝Pfc+Prc+Ps (23)
In the formula: pP＝Pt-PrAnd outputting power for the driving wheels of the vehicle. According to the formula (3), the output power of the vehicle driving wheel includes the rolling resistance power loss of the vehicle driving wheel and the roller of the dynamometer and the power loss of the transmission system of the dynamometer besides the absorption power of the dynamometer.
The traditional measurement mode is to test the output power of the driving wheel by converting kinetic energy absorbed by the dynamometer into electric energy. The invention carries out the measurement of the output power of the driving wheel by installing a rotating speed torque sensor on a connecting shaft of a roller of the dynamometer and measuring the relevant variable of the movement of the roller. Under the working condition that the vehicle runs at a constant speed, a torque balance method is adopted for measuring the output power of the driving wheel of the vehicle, a sensor is adopted for measuring the torque and the rotating speed of the roller, the output power of the driving wheel is calculated through the product of the torque and the rotating speed, the roller of the dynamometer is subjected to stress analysis in a torque balance state, and the torque balance equation can be obtained as shown in the formula (4).
TD＝TP-Tfc＝Trc+Tl (24)
In the formula: t isDThe dynamometer drum being subjected to the driving torque of the vehicle drive wheels, TPIs the actual output torque of the driving wheel, TfcRolling friction resistance torque between wheel and drum, TrcMoment of resistance, T, of dynamometer drive systemlLoading resisting moment T of dynamometer loading motor to rollerlThe force analysis is shown in fig. 1.
At the moment, the rotating speed of the roller of the chassis dynamometer and the rotating speed of the wheels reach a balanced state, the rollers are in a uniform rotating state, and the wheels and the roller do not slide relatively, so that the output power of the driving wheel is equal to
PP＝TP·ω＝(Trc+Tl+Tfc)·ω (25)
In the formula, PPAnd omega is the rotating speed of the roller for outputting power of the driving wheels of the vehicle.
When the vehicle is in a variable speed driving state, the torque balance method cannot be applied. The output power of a vehicle driving wheel at any moment is measured under the variable-speed running working condition of the vehicle, the driving torque and the roller resistance torque of a power measuring machine roller of the vehicle driving wheel are unbalanced due to certain angular acceleration of the wheel and the roller, and the system reaches a balanced state after adding a reverse inertia torque according to the Dalnobel principle, wherein the moment equation at the moment is as follows:
TD-(Trc+Tl)＝TP-(Tfc+Trc+Tl)＝Jα (26)
wherein J is the rotational inertia equivalent to the roller of the chassis dynamometer transmission system, alpha is the angular acceleration of the dynamometer roller, J alpha is the inertia moment, the chassis dynamometer roller stress analysis diagram is shown in FIG. 2, and the driving force power output from the vehicle driving wheel to the roller is expressed by formula (4).
PP＝(Tfc+Trc+Tl+Jα)·ω (4)
A method for measuring the instantaneous output power related variable of a driving wheel.
A method for measuring the rotation speed and torque of a roller.
Through the formula (4), the instantaneous power output by the driving wheels of the vehicle and the resistance torque T borne by the roller are found under the condition that the vehicle does not run at a constant speedfc+Trc+TlThe chassis dynamometer is also related to the rotation speed omega of the roller, the angular acceleration alpha of the roller and the rotational inertia J equivalent to the roller of a chassis dynamometer transmission system, and the rotational inertia J equivalent to the roller is very large due to the complex structure of the chassis dynamometer, the roller and a connecting shaft thereof, a gear box and a simulated resistance loading motor. So that when the drum is in an unbalanced state, the chassisThe drive torque differs significantly from the drum drag torque, so the effect of the drum angular acceleration must be taken into account.
The drum rotation speed omega can be obtained by a magnetoelectric rotation speed torque sensor, the basic principle is as shown in figure 2, and the measured torque and the rotation speed are converted into two groups of alternating current signals with phase difference through an elastic shaft and two groups of magnetoelectric signal generators.
The two sets of alternating electrical signals have the same frequency and are proportional to the rotational speed of the shaft. The rotating speed of the rotating shaft is low, and the signal pulse period is measured by adopting a periodic method. Within m periods t of the rotating speed pulse signal, the pulse period of the crystal oscillator with constant frequency is t0And counting the standard clock pulse signals to obtain n, calculating the period of the rotating speed pulse signals, and calculating to obtain the rotating speed omega.
Where t is the period of the tacho pulse, t0Is a standard clock pulse signal period.
The phase difference of the two groups of alternating current signals and the variation of the phase difference when the two groups of alternating current signals are not loaded form a positive ratio with the torque transmitted by the shaft, and the two groups of alternating current signals can be processed to accurately obtain the torque. When a certain torque is applied to two ends of the sensor, the elastic shaft generates elastic deformation, according to the knowledge of material mechanics, the deformation degree of the shaft is in direct proportion to the magnitude of the torque applied to the two ends of the shaft, when the elastic shaft is not subjected to the torque, the initial phase angle is pi, when the elastic shaft is subjected to the torque change, the two gears generate relative angular displacement, the relative angular change amount of each gear is phi, and the torque causing the angular change is rolling friction resistance torque T between the wheel and the rollerfcResistance moment T of dynamometer transmission systemrcAnd the loading resistance moment T of the dynamometer loading motor to the rollerlSum, i.e. Tfc+Trc+Tl＝TsIndicating torque for the sensor, then φ may be expressed as
Where φ is the change in phase difference of the induced electromotive forces generated by the two coils, L is the working length of the elastic axis of the sensor, G is the elastic modulus of the elastic axis, and J issThe rotational inertia of the elastic shaft, k is the number of teeth of the signal gear, and the above parameters are related to the structural properties of the sensor per se and are known quantities.
The roller rotation angular acceleration measuring method comprises the following steps:
the measuring method of the angular acceleration of the roller is that the tooth number k of a sensor signal gear is known, the angle difference between every two adjacent gears is 2 pi/k, and the time used between the i-th gear and the i + 1-th gear is set as delta tiAt time Δ tiThe average speed of the rollers in the segment is omegai＝θ/△tiThe time taken between the (i + 1) th and (i + 2) th teeth is Deltati+1At Δ ti+1The average rotation speed of the drum in a time period is omegai+1＝θ/△ti+1The average angular acceleration of the cylinder during this period being
Is expressed as due to Δ tiThe time is very short, can
Regarded as the vehicle at Δ tiAcceleration a ofi。
The measuring method of the moment of inertia of a transmission system of the chassis dynamometer and the instantaneous output power of a driving wheel comprises the following steps:
during the operation of the dynamometer, the accuracy of the measurement value of the rotational inertia of the transmission system of the chassis dynamometer is the key for accurately simulating the running resistance of the vehicle. The traditional secondary loading sliding method is to measure the rotational inertia equivalent to a roller of a vehicle transmission system and a dynamometer transmission system and the frictional resistance of the chassis dynamometer and the vehicle transmission system by respectively carrying out two different loading resisting moments on the chassis dynamometer according to an energy conservation law.
The conventional test procedure is as follows:
(1) first, a no-load sliding is carried out [12 ]]Measuring the reverse towing test vehicle at v0The experimental vehicle is accelerated to v on the single-roller chassis dynamometer by the resistance moment under the speed driving condition1，v1Slightly higher than the speed point v to be measured0Storing the kinetic energy of the experimental vehicle during running by the dynamometer, then cutting off the power source of the experimental vehicle, allowing the vehicle to slide under the combined action of the rolling and sliding resistance of the tire and the resistance of the transmission system of the dynamometer, and allowing the vehicle to slide to v2，v2Slightly lower than the speed v to be measured0Recording the sliding distance of the vehicle
Wherein v is1、v2And v0Satisfy v0＝(v1+v2) 2, according to the energy conservation principle of the vehicle in the process of sliding on the single roller, a mathematical model can be obtained
In the formula (I), the compound is shown in the specification,
speed to be measured v0Test of the frictional resistance torque T of the drive train of a vehiclerRolling resistance T between driving wheel and rollerfcSelf internal resistance moment T of chassis dynamometerrcThe sum of the total weight of the components,
vehicle on chassis dynamometer drum from v1Slide to v2The sliding distance, r is the radius of the dynamometer roller, theta is the distance from v on the chassis dynamometer roller1Slide to v2Angle of rotation, J1For the transmission system of the vehicle to be testedAnd the sum of the rotational inertia of all the rotating parts on the chassis dynamometer equivalent to the connecting shaft of the roller of the dynamometer.
(2) The experimental vehicle runs on a roller of a chassis dynamometer and is accelerated to v1At the moment, the rotating speed of the roller is omega1Then cutting off the power system of the vehicle, and simultaneously loading the resistance torque T to the experimental vehicle through the dynamometer motor1At this time, the vehicle is loaded with the resisting moment T1Frictional resistance torque T of vehicle transmission systemrRolling friction resistance torque T between roller and wheelfcAnd dynamometer drive system moment of resistance TrcUnder the combined action of the two wheels, when the vehicle slides to the speed v2At the moment, the rotating speed of the roller is omega2Recording the sliding distance s1And finishing the first sliding.
(3) In the second sliding process, the dynamometer loads a load different from T to the experimental vehicle1Loading resisting moment T2While ensuring the initial speed v during the sliding process1And the final velocity v2The glide distance s2 is recorded as it remains with the first load glide.
(4) Due to the velocity v1、v2And v0Basically, friction resistance generated by the single-roller chassis dynamometer can be approximately considered to be equal when the three speeds run, and a mathematical model is established by utilizing the kinetic energy theorem:
in the formula, T1The first loading slip is the loading resisting moment of the dynamometer to the roller, T2The second load slip being the loading resisting moment, theta, of the dynamometer on the cylinder1For a loading moment of T1In the case of a vehicle driven from v on the chassis dynamometer drum1Slide to v2Angle of rotation, θ2For a loading moment of T2In the case of a vehicle driven from v on the chassis dynamometer drum1Slide to v2The rotated angle can be obtained through an equation set;
in the traditional secondary loading sliding method test process, because the back-dragging sliding is the actual vehicle,
the method comprises the steps of testing the resistance moment of a transmission system of the vehicle, subtracting the friction resistance moment equivalent to a roller connecting shaft from the vehicle transmission system, and accurately detecting the mathematical model [ J ] of the output power of the vehicle driving wheel indoors]Mechanical design and study 2017, 33 (8): 146-,
where α is 15% and (1- α) is the transmission efficiency of the vehicle chassis transmission system.
Calculating the vehicle running at v according to the model0Moment of time drive wheel output torque TPIn order to realize the purpose,
firstly, the test is carried out by adopting the traditional secondary loading sliding method, and firstly, the tested moment of inertia J is obtained by carrying out back-dragging loading sliding on the experimental vehicle1The method comprises the moment of inertia equivalent to a roller of a vehicle transmission system, is not the moment of inertia of a chassis dynamometer system, and cannot accurately eliminate the influence of the loss power of the vehicle transmission system on a measurement result; secondly, in the traditional secondary loading sliding method, the frictional resistance generated by the single-roller chassis dynamometer when the three speeds run can be approximately regarded as equal in the test processThe change of the friction torque of the transmission system of the dynamometer caused by the change of the rotating speed of the roller is not considered; thirdly, only the moment balance of the roller in a balanced state is considered, the actual loading sliding process is a speed changing process, the inertia moment of the roller shaft is not considered, and the model and the measurement result are not accurate enough due to the reason.
In order to effectively eliminate the influence of the rotational inertia of a vehicle transmission system on the measurement of the equivalent rotational inertia of a dynamometer transmission system, a method for measuring the secondary loading sliding of a trailer by anti-dragging simulation is provided.
The improved test process is as follows:
(1) firstly, a general-purpose axle-distance-adjustable trailer is manufactured as shown in fig. 3, weights with different masses are carried on the trailer to meet vehicle types with different masses, meanwhile, the positions of the weights can be adjusted to simulate the gravity center positions of different vehicle types, the trailer is used for accurately measuring the equivalent rotational inertia of the dynamometer, and meanwhile, the influence of the friction torque of a vehicle transmission system on the measurement of the output power of a driving wheel is avoided.
(2) The chassis dynamometer is used for reversely dragging the trailer which has the same mass and the same gravity center position as the trailer to be measured until the speed reaches v, wherein v is greater than the speed v to be measured0Storing kinetic energy of the trailer during running through a chassis dynamometer, and then loading a resistance torque T to the test trailer1Trailer at drag torque T1Rolling friction resistance torque T between roller and wheelfcAnd the resistance moment T of the transmission system of the dynamometerrcSlide under the combined action of the two components to acquire the rotating speed omega of the roller of the dynamometer0＝v0/r and angular acceleration a at the time of the rotational speed1And finishing the first sliding experiment of the trailer reversely towed.
(3) Carrying out the 2 nd sliding, and loading a load different from T to the experimental vehicle by a chassis dynamometer1Loading resisting moment T2Collecting the rotation speed omega of the dynamometer roller0＝v0/r and angular acceleration a at the time of the rotational speed2And establishing a mathematical model by using the angular momentum theorem.
In the formula, alpha1Angular speed ω of the cylinder during the first load sliding0Angular acceleration of time, α2Angular speed ω of the cylinder during the second loading stroke0The angular acceleration of (a). The equivalent rotary inertia J of the dynamometer transmission system to the roller is shown as formula (14), and omega is calculated simultaneously0The sum T of the rolling friction moment between the wheel and the roller and the moment of resistance of the transmission system of the dynamometer at the momentfc+TrcAs shown in formula (15),
(4) the instantaneous output power and the output torque of the vehicle driving wheel can be obtained according to the formula (4) and the formula (14) by measuring the instantaneous output power of the vehicle driving wheel as shown in the formula (16)
In the formula, TsThe torque value is recorded by the sensor, and the torque value is loaded to the dynamometer and the rolling friction torque T between the roller and the wheelfcAnd dynamometer drive system moment of resistance TrcAnd (4) summing.
Constructing a driving wheel instantaneous output power measuring system:
the single-roller chassis dynamometer is used as a test platform, the asynchronous electric dynamometer is used as a road simulation resistance loading device of the vehicle, and the integration of vehicle chassis output power measurement and back dragging can be met. The method comprises the following steps of arranging a rotating speed torque sensor on a connecting shaft of a power measuring machine roller, connecting the rotating speed torque sensor with a power measuring machine transmission system, directly measuring the rotating speed, the torque and the angular acceleration of the power measuring machine roller through the sensor, processing a measurement signal, and transmitting the processed measurement signal to a power measuring machine control system, and calculating through a mathematical model provided by the invention to obtain the instantaneous output power and the output torque of a vehicle driving wheel; meanwhile, the output torque is loaded on the motor as the vehicle road running simulation resisting torque, necessary data is provided for simulating the vehicle road running condition, and a system structure schematic diagram is shown in fig. 4.
The sensor and the signal acquisition and processing system take STM32 as a core, a signal gear in the rotating speed torque sensor sends two paths of voltage signals similar to sine waves along with the rotation of a roller, the two paths of signals are converted into two paths of square signals which have the same frequency as the signal gear and the duty ratio of 50% through a filtering, amplifying and shaping circuit, and one path of signal square signals is transmitted to STM32 as an input signal to measure the rotating speed; the two signals pass through a bistable trigger (74 LS74 is selected) to obtain phase difference pulse signals, and the phase difference pulse signals are transmitted to an STM32 to carry out roller torque measurement; according to equation (7), Δ t is continuously measured for the measurement of angular accelerationiSetting a counter to trigger counting for rising edges, and acquiring delta t by capturing and recording the rising edges of square signals by using a single chip microcomputeriContinuously measuring and recording Δ tiThe value of (3) can record the jump moment without additional operation of a CPU (central processing unit), thereby saving the interrupt processing time and creating conditions for continuously measuring the pulse width of the square wave signal. Each square wave period of the speed signal can be obtained by continuously capturing the up-jump of the input speed signal. According to the pulse width of square waves at any two adjacent moments, the average angular acceleration in two adjacent time periods can be calculated through a single chip microcomputer according to a formula (29), a signal acquisition and processing system is shown in fig. 5, and STM32 transmits acquired rotating speed, torque and angular acceleration signals to an industrial personal computer through serial port communication MAX 232.
Analysis and verification of experimental results
A single-roller chassis dynamometer of a type AVL Road-sim 48' produced by AVL company is adopted to carry out chassis driving wheel output power test on Jiangling Baodian diesel oil driving vehicles, and the roller radius r of the dynamometer is 0.61 m. By adopting the measuring method provided by the invention, the trailer of the simulated Baodian vehicle is reversely towedLoading and sliding, the loading resistance torque value is T 1100 N.m and T2Set v at 50N m0＝100km/h、v0＝80km/h、v0Adopting improved secondary loading sliding method to respectively measure the angular acceleration alpha of the roller of the dynamometer under the condition of two loading resistances as three speed points to be measured of 60km/h1And alpha2Five tests are carried out, and the average values are respectively taken and recorded
And
the moment of inertia of the drive train of the chassis dynamometer is calculated according to equation (2) and the results are shown in table 1.
TABLE 1 improved quadratic loading sliding experimental data and equivalent rotary inertia of chassis dynamometer obtained by the same
The equivalent rotary inertia of a chassis dynamometer transmission system to a roller is calculated through data acquired by a sliding experiment and a mathematical model provided by the invention, and the obtained rotary inertia is averaged to obtain the average value J which is 458.7 kg.m2According to official data supplied by Jiangling company [14 ]]The equivalent mass of the AVL Road-sim48 dynamometer is 1178kg, and because the experiment process actually simulates the sliding of a trailer, the equivalent rotary inertia of a vehicle tire to a roller is needed, and the equivalent rotary inertia of the total weight of a dynamometer chassis transmission system and a Jiangling Baodian automobile tire to the roller is 454.2kg m.2The measurement error is 1%, and the equivalent rotational inertia value is calculated by the driving wheel output power experimental model by adopting the secondary loading sliding data in consideration of factors such as tire air pressure and deformation in the driving process.
Testing the instantaneous output power of the driving wheel in the process of accelerating the vehicle, averagely setting 5 speed points to be tested in a running speed range of 80 km/h-100 km/h, and arranging the speed points on a rollerSensor on drum connecting shaft for measuring drum rotating speed omega and sensor indicating torque TsAnd the roller rotation angle acceleration alpha, and calculating the instantaneous output power P of the driving wheel by the formula (5)PAnd outputting driving torque, wherein the measured data and the model calculated value are shown in the table 2.
TABLE 2 test variables at different speed points and instantaneous output power of driving wheel calculated according to digital-to-analog
In order to perform comparison and analysis of experimental data, a driving wheel output torque model obtained by a calculation model and a vehicle road experiment is respectively compared and analyzed with the driving wheel instantaneous output torque obtained by the method, wherein road sliding experimental data are official data provided by Jiangling company, and the driving wheel output power is a calculation result of multiplying the road running resistance by the vehicle speed.
TABLE 3 comparison of drive wheel output power and torque data obtained from different models
In table 3, the driving wheel output torque calculated by using the mathematical model established by the conventional secondary loading coasting method is TP'Driving wheel output Power is P'P(ii) a The road running resistance moment of the vehicle is TroadThe output power of the driving wheel obtained by the vehicle road sliding experiment is ProadThe driving wheel output torque and the road running resistance torque of the two models at different vehicle speeds are shown in fig. 3.
According to the analysis of FIG. 6, in the driving speed interval of 80 km/h-100 km/h, the output torque of the driving wheel of the vehicle is gradually increased and the output power of the driving wheel is also gradually increased along with the increase of the vehicle speed; the driving wheel output torque obtained by the experimental method and the mathematical model provided by the invention is closer to a road running resistance model, and the road running resistance can be more effectively simulated in the process of simulating the road running of the vehicle by the dynamometer; meanwhile, the output power of the obtained driving wheel is closer to the road running condition, and the precision of the test result is higher.
In order to further analyze the model accuracy, the driving wheel output torque and the road running resistance torque obtained by the conventional method and the method of the invention are compared with each other by taking the road running resistance torque as a reference, so as to obtain the relative error of the driving wheel output power of the two models relative to the road running model, and the result is shown in fig. 4.
According to the analysis of FIG. 7, in the running speed interval of 80 km/h-100 km/h, the output torque of the driving wheel obtained by adopting the model is TP' road running resistance torque with vehicle is TroadWhen the vehicle speed is 100km/h, the error is 4.2 percent at most, when the vehicle speed is 80km/h, the error is 2.2 percent at least, the measurement error is influenced by the running speed of the vehicle, and the measurement error is gradually increased along with the increase of the vehicle speed; the driving wheel output torque obtained by adopting the model of the invention is TPThe running resistance moment of the vehicle on the road is TroadThe relative error of the driving wheel is far smaller than that of the traditional method, the maximum relative error is 0.63%, the mathematical model of the output power of the driving wheel established by the invention can basically reflect the actual road running condition, and the relative error is not influenced by the running speed of the vehicle.
In conclusion, aiming at the problem that the measurement precision of the instantaneous output power of the vehicle driving wheel by the chassis dynamometer is insufficient in the traditional test method, a measurement system for the variables such as the rotating speed, the torque and the angular acceleration of the roller of the dynamometer is constructed. On the basis, a vehicle driving wheel instantaneous output power model is established, and a vehicle driving wheel instantaneous power measuring method is researched.
(1) The method for performing the anti-drag sliding test on the simulated trailer by adopting the secondary loading sliding method is provided, the equivalent rotary inertia of the chassis power measuring machine is accurately calculated and obtained by testing the experimental data of the rotary speed, the angular acceleration, the torque and other variables related to the movement of the rotary drum, the influence of a vehicle chassis transmission system on the measurement result in the traditional test method is effectively avoided, the error caused by the fact that the output power of the driving wheel is calculated by adopting an empirical formula in the traditional test method is overcome, the error between the equivalent rotary measurement result of the power measuring machine obtained by the method and official data is only 1 percent, the effectiveness of the method is proved, and accurate parameter values are provided for the accurate measurement of the instantaneous output torque of the driving wheel.
(2) By analyzing the stress condition of the vehicle running on the roller of the dynamometer and establishing a mathematical model of the instantaneous output power of the driving wheel of the vehicle according to the law of conservation of angular momentum, and analyzing the model and variables, compared with the traditional model, all original data in the model are directly measured by a sensor, so that the defect that the measurement result is provided with errors when the internal resistance moment of the dynamometer is used as constant force modeling in the traditional method is overcome, and the calculation process is simple and convenient; in a running speed range of 80 km/h-100 km/h, in a test experiment of the output torque of the vehicle driving wheel, the maximum relative error is 0.63%, the error of a traditional model is effectively reduced by 2.2% -4.2%, the output torque of the driving wheel obtained by the model is closer to the output torque of the driving wheel in a vehicle road test, and accurate data are provided for a dynamometer to accurately simulate the running resistance of the vehicle road.
(3) The driving wheel output power obtained by the mathematical model established by the invention is not influenced by the driving speed of the vehicle by taking the driving wheel output power of the vehicle road driving experiment as a reference, the defect that the calculation error is gradually increased along with the increase of the vehicle speed in the traditional model is overcome, and the precision of the measurement result is not influenced by the driving speed of the vehicle. The power value obtained by the model can more accurately reflect the instantaneous power value of the driving wheel, the measurement precision is greatly improved compared with the traditional method, and a theoretical basis is provided for the accurate disassembly-free rapid detection of the output power of the driving wheel of the vehicle.
Although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
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| CN115096507A (en) * | 2022-05-10 | 2022-09-23 | 中国第一汽车股份有限公司 | A method for measuring the moment of inertia of a passenger car drive train |
| CN114942384B (en) * | 2022-05-27 | 2024-11-15 | 中检西部检测有限公司 | Electric vehicle motor test method |
| CN115096621B (en) * | 2022-06-15 | 2023-03-14 | 中南大学 | Power parasitic detection method and device for walking wheels of straddle type monorail vehicle |
| CN115046664B (en) * | 2022-08-16 | 2022-11-15 | 山东新凌志检测技术有限公司 | Chassis dynamometer with adjustable single-roller four-wheel-drive wheelbase |
| CN117890128B (en) * | 2024-03-14 | 2024-05-31 | 中汽研汽车检验中心（天津）有限公司 | Method for testing running resistance of heavy vehicle under any load |
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