CN100516802C - Inertia determination of automobile - Google Patents

Abstract

A method for determining inertia of automobile includes measuring out curve of taxing speed to time of automobile on flat road and taking out time t in taxing a linear section of V1 to V2 , measuring out resistance torque curve of automobile taxing under the same condition as measuring out said curve, obtaining rotary inertia of matched test machine on power assembly system, carrying out loading by loader of said test machine according to measured resistance torque curve to measure out time t in the same rotation variation section of V1 and V2 for obtaining inertia of measured automobile.

Description

The assay method of automobile inertia

Technical field

The present invention relates to a kind of assay method of automobile inertia, especially design a kind of power assembly system matching test bench that utilizes automobile inertia is carried out method for measuring.

Background technology

In the Automobile Detection field, generally adopt two kinds of methods to measure automobile inertia at present, below these two kinds of methods are briefly described.

1) calculates automobile inertia by experimental formula.

Experimental formula commonly used is:

$I=\frac{{\mathrm{Wr}}^2}{2g}$

Wherein, W is the two-wheel assumed (specified) load, and r is the rolling radius of wheel, and g is the gravity acceleration constant.

Wherein, W can calculate by following manner:

W＝K(G ₀+2600)

Wherein, K is a correction factor, K=0.86

G ₀Empty wagons load, the i.e. suffered load of detent during empty wagons.

The shortcoming of utilizing above-mentioned experimental formula be calculate very coarse, can not be exactly on stand the actual operating mode of simulation.

2) measure the rotary inertia of automobile barycenter and each rotatable parts by physical pendulum method, three-way suspension etc., further, carry out mathematical modeling according to Location of Mass Center of Automobiles, obtain its frequency spectrum by actual road test then, again the frequency spectrum that obtains is analyzed, obtained the moment of inertia of automobile around its barycenter according to the analysis result of frequency spectrum.The shortcoming of this method is that process is very complicated, and needs some special equipment, and cost is very high.

The power assembly test-bed is used for full test engine characteristics and every function, whether can reach designing requirement with its car load power performance and every index after assessment and the entrucking of prediction engine, this has become an indispensable very important ring in the research automobile process.Generally, as shown in Figure 1, the power assembly test-bed comprises dynamometer machine, speed reduction unit, torque sensor, engine (and wheel box), and each parts uses the shaft coupling such as metallic laminations shaft coupling, the special-purpose shaft coupling of engine to connect.What deserves to be mentioned is that dynamometer machine is widely used in the field tests of automotive performance, can measured automobiles driving wheel output power, moment of torsion (or driving force) and rotating speed data such as (or speed), and these data presentation are come out.

Summary of the invention

The objective of the invention is to solve and calculate coarse and calculation of complex in the prior art, and the higher shortcoming of cost, provide a kind of calculating accurately/simply, and the lower-cost method that vehicle inertia is converted and simulated.

The invention provides a kind of conversion and analogy method of automobile inertia, comprise step: speed is taken out this curve medium velocity and is changed one section comparatively linear V with respect to the curve of time when a) measuring real vehicle and sliding when the smooth-riding surface ₁To V ₂The time t that is experienced; And measure the damping moment curve when automobile slides in this smooth-riding surface under the similarity condition; B) obtain the moment of inertia I of power assembly system matching test bench _εC) loader on the described stand loads according to the damping moment curve that records, and records same rotation speed change section V ₁To V ₂The time t of experience _v, obtain the inertia of tested automobile $I_v=\frac{t}{t_v}{I}_{\mathrm{\ϵ}}.$

The method that vehicle inertia is converted and simulated provided by the invention has to be calculated accurately, and owing to only need simple equipment with low cost, thereby have lower-cost advantage.

Description of drawings

Fig. 1 is the structural representation of power assembly testing table;

Fig. 2 is the structural representation that the power assembly testing table of flywheel is installed.

Embodiment

Introduce the specific embodiment of the present invention below in detail.

Automobile inertia conversion provided by the present invention and analogy method comprise step: a kind of conversion of automobile inertia and analogy method, comprise step: speed is taken out this curve medium velocity and is changed one section comparatively linear V with respect to the curve of time when a) measuring real vehicle and sliding when the smooth-riding surface ₁To V ₂The time t that is experienced; And measure the damping moment curve when automobile slides in this smooth-riding surface under the similarity condition; B) obtain the moment of inertia I of power assembly system matching test bench _εC) loader on the described stand loads according to the damping moment curve that records, and records same rotation speed change section V ₁To V ₂The time t of experience _v, obtain the inertia of tested automobile $I_v=\frac{t}{t_v}{I}_{\mathrm{\ϵ}}.$

For step a), can utilize speed detector, for example the vehicle speed sensor that is connected with computer is measured vehicle speed curve over time on the smooth-riding surface, and storage or show is on computers then taken out this curve medium velocity again and changed one section comparatively linear V ₁To V ₂The time of being experienced.So-called " smooth-riding surface " is meant that vehicle friction force between road surface and the vehicle when sliding is comparatively constant; So-called " comparatively linear " is meant that described slope of a curve (being the acceleration of automobile) is in certain scope, can not cause a kind of approximation method of huge deviation in computation process, and this method is used for common engineering calculation or signal Processing.In addition, can utilize common chassis dynamometer to record the damping moment curve of automobile.

For step b), obtain the moment of inertia I of power assembly system matching test bench _εMultiple existing method is arranged, and the data that for example can utilize described stand manufacturer to provide obtain by simple computation.Under the preferable case, obtain the moment of inertia I of this stand _εComprise step:

Step b1), the loader on the described stand is with certain torque T ₁To rotation speed n, test the time t of experience from 0 towing astern ₁

Step b2) this loader is with certain torque T ₂To rotation speed n, measure the time t of experience from 0 towing astern ₂

Step b3), utilize known calculating process:

$\begin{array}{c}{T}_1-T_z=2\mathrm{\π}{I}_{\mathrm{\ϵ}}\·\frac{\mathrm{dn}}{{\mathrm{dt}}_1}\\ T_2-T_z=2\mathrm{\π}{I}_{\mathrm{\ϵ}}\·\frac{\mathrm{dn}}{{\mathrm{dt}}_2}\end{array}$ (T _zBeing the moment of resistance of described stand, is a measurement)

The inertia that obtains described stand is:

$I_{\mathrm{\ϵ}}=\frac{T_1-T_2}{2\mathrm{\πn}(t_2-t_1)}{t}_1{t}_2$

The derivation of The above results is as follows:

$T_1-T_2=2\mathrm{\π}{I}_{\mathrm{\ϵ}}(\frac{\mathrm{dn}}{{\mathrm{dt}}_1}-\frac{\mathrm{dn}}{{\mathrm{dt}}_2})$

T ₁And T ₂Because of this adopts bigger value, speed n then can not be too high, so just can change to n from 0 with very big acceleration, thereby guarantee that described acceleration has better linearity.

Because acceleration is very big, can thinks that therefore the variation from 0 to n of top equation medium velocity is linear, thereby obtain following equation:

$T_1-T_2=2\mathrm{\π}{I}_{\mathrm{\ϵ}}n(\frac{1}{t_1}-\frac{1}{t_2})\⇒I_{\mathrm{\ϵ}}=\frac{(T_1-T_2)}{2\mathrm{\πn}(t_2-t_1)}{t}_1{t}_2$

Introduce step c) and derivation thereof below in detail.

Because the loader on the described power assembly system matching test bench is (step a)) that loads according to the damping moment curve that slides with the formula car, therefore the torque that loads on torque on the tested automobile and the described stand equates, promptly

I _vω _v＝I _εω _ε

Wherein, ω _vAnd ω _εBe respectively the angular acceleration of the automobile that records by chassis dynamometer and the angular acceleration on the stand, and this two angular acceleration values all is the speed interval V that changes at approximately linear ₁To V ₂Between record, so this two accekerations also are approximately linears, thereby obtain,

$I_v\·\frac{2\mathrm{\π}(V_2-V_1)}{t_v}=I_{\mathrm{\ϵ}}\·\frac{2\mathrm{\π}(V_2-V_1)}{t}\⇒I_v=\frac{t}{t_v}{I}_{\mathrm{\ϵ}}$

Above-mentioned process can only be derived the inertia of automobile from the mathematics angle, and can not in the operation of reality, automobile inertia be simulated, therefore, for can be in practical operation the inertia of simulated automotive, need on the power assembly system matching test bench, increase the inertia of flywheel.

As shown in Figure 2, flywheel is connected between dynamometer machine output shaft and the speed reduction unit, utilizes the metallic laminations shaft coupling to be connected with the two, and utilizes any available flywheel fastener, and for example the flat key (not shown) is fixed.When engine drives this flywheel rotation, can from dynamometer machine, read desired parameter.

Under the preferable case, method provided by the invention further comprises step d), increases flywheel on described stand, and the inertia of this flywheel is $I_f=(\frac{t}{t_v}-1)I_{\mathrm{\ϵ}}.$

Increase after the flywheel inertia, then can be on described stand the inertia of simulated automotive, the inertia derivation of described flywheel is:

$I_f=I_v-I_{\mathrm{\ϵ}}=(\frac{t}{t_v}-1)I_{\mathrm{\ϵ}}$

Claims (4)

1. the assay method of an automobile inertia comprises:

Speed is taken out this curve medium velocity and is changed one section comparatively linear V with respect to the curve of time when a) measuring real vehicle and slide when the smooth-riding surface ₁To V ₂The time t that is experienced; And measure the damping moment curve when automobile slides in this smooth-riding surface under the similarity condition;

B) obtain the moment of inertia I of power assembly system matching test bench _ε

C) loader on the described stand loads according to the damping moment curve that records, and records same rotation speed change section V ₁To V ₂The time t of experience _v, obtain the inertia of tested automobile $I_v=\frac{t}{t_v}{I}_{\mathrm{\ϵ}}.$

2. method according to claim 1, wherein, one section of described comparatively linearity is meant the line segment of slope within preset range.

3. method according to claim 1, wherein, described step b) comprises:

B1), the loader on the described stand is with torque T ₁To rotation speed n, test the time t of experience from 0 towing astern ₁

B2) this loader is with torque T ₂To rotation speed n, measure the time t of experience from 0 towing astern ₂

B3), the inertia that obtains described stand is $I_{\mathrm{\ϵ}}=\frac{T_1-T_2}{2\mathrm{\πn}(t_2-t_1)}{t}_1{t}_2.$

4. method according to claim 1, wherein, this method further comprises d), on described stand, increasing flywheel, the inertia of this flywheel is $I_f=(\frac{t}{t_v}-1)I_{\mathrm{\ϵ}}.$

Images