CN102941875A - Estimation method for angle of steering wheel of electric power steering system - Google Patents

Abstract

The invention discloses a measuring method for an angle of a steering wheel of a torque sensor for a single measuring torque signal. According to the method, the angle of the steering wheel is quickly and accurately estimated, without adding a steering wheel angle sensor. The method comprises the following steps: (1) calculating Omega (t) according to a formula (1): Omega (t)=ig*Nm(t), wherein the Omega (t) is an angular velocity at t moment, the ig is a reduction ratio and the Nm(t) is a rotating speed of an assisting motor of an electric power steering system at the t moment; and (2) calculating Theta (t) according to a formula (2), wherein tsample is the sampling time and the Theta (t) is the angle of the steering wheel of the electric power steering system at the t moment.

Description

A kind of evaluation method of electric boosting steering system steering wheel angle

Technical field

The present invention relates to automobile electrically-controlled technical field, relate in particular to a kind of evaluation method of electric boosting steering system steering wheel angle.

Background technology

Electric boosting steering system (Electric Power Steering is called for short EPS) generally is comprised of sensor, ECU, actuating motor.Sensor obtains corresponding signal (such as ignition signal, steering wheel torque, angle signal, vehicle speed signal) and reaches ECU, and then ECU calculates by analysis, sends to assist motor and drives order, realizes Power assisted control.Simultaneously, motor also can to ECU feedback current voltage or tach signal, be realized closed loop control.Details are seen Fig. 1.

The merchant of Wuhan University of Technology is peaceful when carrying out the EPS technological analysis, and torque sensor is classified as first of the EPS critical component.Torque sensor has contact and contactless two kinds by physical construction classification, in general the two can direction of measurement dish torque signal, but can not realize the measurement of steering wheel angle and rotating speed according to the lower contact torque sensor of price that the difference of its inside principle has.

The Geng Xiaohua in building up with Shandong University of Dalian University of Technology has all adopted the differential transformer type torque sensor in EPS design separately, to realize the measurement of moment of torsion and angle.Zhao Mingxiang has then invented a kind of band steering wheel angle and has calculated and compensated the electric booster steering device control method.He adopts the variation of hall sensor induced flux, produce corresponding impulse singla, by becoming the square wave of standard after the shaping circuit processing, sending into electronic control unit processes, electronic control unit analyzes the rotation direction of bearing circle according to torque signal, simultaneously square-wave signal is carried out positive and negative accumulative total, calculate the turned angle of bearing circle, the square wave signal-count is calculated the rotating speed of bearing circle.The bearing circle acquisition scheme of three employings is seen shown in the scheme one among Fig. 2.

What above-mentioned researcher adopted all is noncontacting proximity sensor direct direction of measurement dish angle and rotating speed.In the engineering of reality is used, EPS producer is for the consideration to cost mostly, and the lower-cost touch sensor of choice for use, these sensors often can only be measured moment of torsion, and can't direction of measurement dish corner and rotating speed, so they propose the evaluation method of empirical equation, see shown in the scheme two among Fig. 3, but these methods need a large amount of verification experimental verifications, and its accuracy real-time all has much room for improvement.

Tianjin Enginnering Normal College's temperature resolves to mention in its research, utilizes in the EPS system hardware existing assist motor signal that the bearing circle rotating speed is estimated, namely utilizes bearing circle rotational speed omega and assist motor rotational speed N _mProportional relation obtains the bearing circle rotating speed.Bearing circle rotational speed omega and assist motor rotational speed N _mProportional pass is:

ω＝i _g*N _m

Wherein, i _gBe reduction ratio.But how further he do not have explanation calculated direction dish angle signal.See shown in the scheme three among Fig. 4.

The scheme one direct employing non-contact torque sensor with rotating speed that can take measurement of an angle can realize the collection of all signals of bearing circle, but cost is higher; Second scheme adopts the evaluation method of contact torque sensor and empirical equation, but the accuracy real-time of evaluation method all remains to be discussed; Scheme three adopts touch sensor, and in conjunction with motor speed N _mCalculated direction dish angular velocity omega, cost is lower, but does not propose the method for calculating of steering wheel angle.

In sum, the lower contact torque sensor of price is used in EPS design, and when not increasing extra steering wheel angle sensor, how calculating rapidly and accurately steering wheel angle is the technical barrier of EPS.

Summary of the invention

For overcoming the defective of prior art, the technical problem to be solved in the present invention has provided in a kind of situation not increasing steering wheel angle sensor the rapidly and accurately evaluation method of electric boosting steering system steering wheel angle.

Technical scheme of the present invention is: the evaluation method of this electric boosting steering system steering wheel angle may further comprise the steps:

(1) calculate ω (t) according to formula (1),

ω(t)＝i _g*N _m(t) （1）

Wherein ω (t) is t cireular frequency constantly, i _gReduction ratio, N _m(t) be the constantly rotating speed of electric boosting steering system assist motor of t;

(2) calculate θ (t) according to formula (2),

$\mathrm{\θ}\left(t\right)=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\mathrm{\ω}\left(t_i\right)*t_{\mathrm{sample}}---\left(2\right)$

T wherein _SampleBe the sampling time, θ (t) is t electric boosting steering system steering wheel angle constantly.

Because this method just can realize by software programming, so do not need to come direction of measurement dish angle with the high non-contact torque sensor of price, and only with the lower contact torque sensor of price and do not increase in the situation of steering wheel angle sensor and just can obtain rapidly and exactly steering wheel angle.

Description of drawings

Fig. 1 is the structural representation of electric boosting steering system;

Fig. 2 is the scheme drawing of scheme one in the prior art;

Fig. 3 is the scheme drawing of scheme two in the prior art;

Fig. 4 is the scheme drawing of scheme three in the prior art;

Fig. 5 is the scheme drawing of method of the present invention.

The specific embodiment

As shown in Figure 5, the evaluation method of this electric boosting steering system steering wheel angle may further comprise the steps:

(1) calculate ω (t) according to formula (1),

ω(t)＝i _g*N _m(t) （1）

Wherein ω (t) is t cireular frequency constantly, i _gReduction ratio, N _m(t) be the constantly rotating speed of electric boosting steering system assist motor of t;

(2) calculate θ (t) according to formula (2),

$\mathrm{\θ}\left(t\right)=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\mathrm{\ω}\left(t_i\right)*t_{\mathrm{sample}}---\left(2\right)$

T wherein _SampleBe the sampling time, θ (t) is t electric boosting steering system steering wheel angle constantly.

Because this method just can realize by software programming, so do not need to come direction of measurement dish angle with the high torque sensor of price, and only with the lower contact torque sensor of price, and in the situation that does not increase steering wheel angle sensor, just can obtain rapidly and exactly steering wheel angle.

The below provides a specific embodiment, and t constantly motor speed is N _m(t), corresponding bearing circle cireular frequency is ω (t)=i _g* N _m(t), steering wheel angle is θ (t).The motor speed sampling time t of ECU _SampleBe between 0.5 μ s～2 μ s, with respect to the rotating speed 500 °/s of chaufeur to bearing circle, this is a very short time.Therefore, with regard to the variation of steering wheel angle, when time t variation was very small, the variation of steering wheel angle was also very small, and namely the variation ω (t) of steering wheel angle is continuous.Therefore, within very short a period of time, the variation of ω (t) is very little, is similar to constant speed, in the very little period, just can calculate the approximate value of steering wheel angle at this section so; In some time section summation, again in conjunction with initial condition (IC), just can get the angle approximate value of whole time period, be the constantly angle θ (t) of bearing circle of t.

Concrete derivation step is as follows:

Rotate beginning with bearing circle by reference position, its rotating speed changes continuously afterwards.Initial condition (IC):

t＝0,ω（0）＝0,θ（0）＝0

Within the time [0, t], motor speed sampling n+1 time obtains n+1 bearing circle cireular frequency successively:

ω（t ₀）,ω（t ₁）......ω（t _n-1）,ω（t _n）,

Wherein:

0≤t ₀＜t ₁＜......＜t _n1＜t _n≤t

And

Δt＝t ₁-t ₀＝t ₂-t ₁＝......＝t _n-t _n-1＝t _sample

The variation of the steering wheel angle of each time period is followed successively by

Δθ ₁,Δθ ₂......Δθ _n-1，Δθ _n

Wherein

Δθ ₁≈ω（t _i）*Δt＝ω（t _i）*t _sample

So the t constantly angle of bearing circle is

$\mathrm{\θ}\left(t\right)=\mathrm{\θ}\left(0\right)+\mathrm{\Δ}{\mathrm{\θ}}_1+\mathrm{\Δ}{\mathrm{\θ}}_2+......+\mathrm{\Δ}{\mathrm{\θ}}_{n-1}+\mathrm{\Δ}{\mathrm{\θ}}_n$

$\≈0+\mathrm{\ω}\left(t_1\right)*t_{\mathrm{sample}}+\mathrm{\ω}\left(t_2\right)*t_{\mathrm{sample}}+......+\mathrm{\ω}\left(t_{n-1}\right)*t_{\mathrm{sample}}+\mathrm{\ω}\left(t_n\right)*t_{\mathrm{sample}}$

$=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\mathrm{\ω}\left(t_i\right)*t_{\mathrm{sample}}$

The above; it only is preferred embodiment of the present invention; be not that the present invention is done any pro forma restriction, any simple modification, equivalent variations and modification that every foundation technical spirit of the present invention is done above embodiment all still belong to the protection domain of technical solution of the present invention.

Claims (1)

1. the evaluation method of an electric boosting steering system steering wheel angle is characterized in that: may further comprise the steps:

(1) calculate ω (t) according to formula (1),

ω(t)＝i _g*N _m(t) （1）

Wherein ω (t) is t cireular frequency constantly, i _gReduction ratio, N _m(t) be the constantly rotating speed of electric boosting steering system assist motor of t;

(2) calculate θ (t) according to formula (2),

$\mathrm{\θ}\left(t\right)=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\mathrm{\ω}\left(t_i\right)*t_{\mathrm{sample}}---\left(2\right)$

T wherein _SampleBe the sampling time, θ (t) is t electric boosting steering system steering wheel angle constantly.

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