CN103439030A - Texture force measuring method in force tactile representation - Google Patents

Abstract

The invention discloses a texture force measuring method in force tactile representation. The texture force is decomposed to an acting force in the vertical direction and an acting force in the horizontal direction by considering surface factors of an objective texture and movement speed and active press force in the exploring process with human hands. The acting force in the vertical direction is divided into an objective factor acting force and a subjective factor acting force, wherein the objective factor acting force is determined by height of a microcosmic contour on the surface of the texture measured and surface stiffness characteristic. In consideration of change of normal acceleration in the contact process reflecting changes of speed and pressure of human hands in the moving process, the subjective factor acting force is the function of the normal acceleration, and the normal acceleration in simulation is a linear interpolation function of the measured acceleration under different pressures and at different speeds. The acting force in the horizontal direction can be frictional resistance when a probe streaks the surface of the texture and is determined by the pressure in the vertical direction and the dynamic friction coefficient of the texture material.

Description

Texture force measuring method in a kind of haptic feedback

Technical field

The invention belongs to the reproducing texture force touch field, relate to a kind of power haptic rendering method of texture.

Background technology

At present, the texture force touch expression technology is mainly set up the power touch model while contacting with grain surface and by the haptic feedback device, the power sense of touch reproduced out according to the contour feature of grain surface.The modeling method that texture based on the haptic device device is expressed mainly is divided three classes: the power haptic rendering model of setting up texture based on geometrical constraint and physical model; The contour feature that extracts grain surface from image is set up power haptic rendering model; The profile of actual measurement real-texture or vibration information, reproduce texture information by virtual reality technology.

The surveying instrument of the texture power expression technology based on the actual measurement model is divided into two kinds: a kind of is contactless, as the three-dimensional optical surface profiler, by optical characteristics, obtains the surface three dimension elevation information.This method is had relatively high expectations to cleanliness and the flatness of measured surface.Another kind is contact, is generally that the mode of by probe, rapping or pressing scans grain surface, and the status information in mutual by sensor record.The subject matter of this method is " indeterminacy ", in system, adds sensor can change original connection status and dynamic perfromance, causes the deviation between measurement result and original case.

For the measurement based on probe scanning grain surface contact, domestic technique generally obtains the force value of probe scanning grain surface by the power sensor, force value directly is expressed as to texture micro-profile height as the device for force feedback power output through simple process, the acceleration signal of the grain surface of measuring probe scanning simultaneously on basis at home in foreign study, improve the validity of texture sense of touch through conversion output.

At present, based on probe measurement grain surface information and be applied to having of haptic feedback: the propositions such as Hari laterally drag on a real-texture surface with SensAblePHANTOM, estimate the displacement disturbance perpendicular to surface direction simultaneously, and set up on this basis a texture power model; Power and acceleration when JochenLang etc. have proposed to measure handheld probe and rap touch texture with the wireless touch sensor of WHaT, and calculate roughness and the rigidity of textures by these measurement results; The propositions such as Okamura are described the acceleration profile of probe when grain surface slides by attenuated sinusoidal signal; The acceleration profile value that the propositions such as Guruswamy are used iir filter to produce is multiplied by zoom factor as texture power; XianmingYe etc. propose with two strainometers and a force sensor measuring three-dimensional force signal, utilize normal force and tangential force to obtain the friction force of texture, and while with piezoelectric membrane, measuring contact probe axial contact stress dynamically read and for the haptic feedback of texture; The propositions such as Joseph are carried out LPC filtering to the acceleration signal collected, and the acceleration signal of prediction is exported by computer sound card, by current amplifier, drive the voice coil motor on the texture pick-up unit to realize the virtual texture haptic feedback.

Summary of the invention

Technical matters: the present invention proposes a kind of role of subjective intentions that utilizes acceleration signal to carry out the texture force modeling and consider the people to the texture force measuring method in the haptic feedback of texture haptic display impact.

Technical scheme: the texture force measuring method in haptic feedback of the present invention comprises the following steps:

In virtual texture power model, utilize the virtual probe that the lever of haptic feedback equipment is controlled in model to streak on the dummy object surface, whether detect virtual probe and dummy object comes in contact simultaneously, and whether relative motion arranged, if virtual probe and dummy object come in contact or without relative motion, virtual texture power

be output as 0, otherwise, virtual texture power calculated according to the following formula

and output:

${\stackrel{\→}{F}}_{\mathrm{con}}={\stackrel{\→}{F}}_{\mathrm{ver}}+{\stackrel{\→}{F}}_{\mathrm{hor}};$

Wherein,

for the vertical direction acting force of virtual texture power, for the horizontal direction acting force of virtual texture power, ${\stackrel{\→}{F}}_{\mathrm{ver}}={\stackrel{\→}{F}}_{\mathrm{obj}}+{\stackrel{\→}{F}}_{\mathrm{sub}};{\stackrel{\→}{F}}_{\mathrm{hor}}=\stackrel{\→}{f},$ Wherein,

for the objective factor acting force,

for the subjective factor acting force,

the suffered horizontal direction friction force of virtual probe during for relative motion;

The objective factor acting force

calculate according to the following formula:

${\stackrel{\→}{F}}_{\mathrm{obj}}=k_1\×k_s\×H\×\stackrel{\→}{n};$

Wherein, k _sa constant describing the texture materials stiffness coefficient, when H is virtual probe perception texture and the corresponding grain surface profile of the contact point height of grain surface, k ₁constant factor,

it is the vertical direction vector of unit length;

Constant k _sbe numerically equal to the linear coefficient A of vertical direction acceleration mean square deviation and pressing force, the computing formula of vertical direction acceleration mean square deviation is:

wherein, N is the group number of measured vertical direction acceleration, a _ibe the vertical direction acceleration information by the actual measurement of texture detecting pen, in order to obtain the linear coefficient A of vertical direction acceleration mean square deviation and pressing force, use correlation analysis and regretional analysis to calculate with pressing force F _p, sweep velocity v is independent variable, with vertical direction acceleration mean square deviation a _rmsfunctional relation for dependent variable: a _rms(F _p, v)=A * F _p+ B * v, wherein, A is vertical direction acceleration mean square deviation a _rmswith pressing force F _plinear coefficient, B is vertical direction acceleration mean square deviation a _rmswith the linear coefficient of sweep velocity v, F _pfor pressing force in the actual measurement process, v is sweep velocity in the actual measurement process; Constant factor k ₁computing formula be

wherein, F _maxfor the maximum power output of actual forces feedback device, constant c ₁value is the arbitrary numerical value in 0.6-0.8;

The subjective factor acting force

calculate according to the following formula:

${\stackrel{\→}{F}}_{\mathrm{sub}}=k_a\×a_{\mathrm{ver}}(F_p,v)\×\stackrel{\→}{n};$

Wherein, a _ver(F _p, v) be pressing force size F arbitrarily in the perception of using the method for linear predictive coding and bilinear interpolation to obtain _pwith the vertical direction acceleration under any perception velocities v, k _afor degree of will speed up signal a _ver(F _p, v) be converted into force signal

constant factor, computing formula is:

Wherein, determine the objective factor acting force

with the subjective factor acting force the constant c of weight ratio ₂value is the arbitrary numerical value in 0.1-0.4, F _objfor the vertical direction acceleration of measured objective factor acting force under any pressing force and exploration speed;

it is the vertical direction vector of unit length;

Described horizontal direction frictional resistance

calculate according to the following formula:

$\stackrel{\→}{f}=\mathrm{\μ}\×\left|F_{\mathrm{ver}}\right|\×\stackrel{\→}{t}$

Wherein, μ is the coefficient of sliding friction of virtual probe when the virtual texture surface sliding, F _verfor texture power vertical direction acting force, for the horizontal direction vector of unit length.

Beneficial effect: the present invention compared with prior art, has the following advantages:

1, use the acceleration signal of actual measurement to carry out the calculating of objective factor acting force, objective factor Calculation of the force formula is:

this formula has embodied the vital role that the objective characteristic of texture is calculated virtual texture power, and wherein, Parameter H has embodied micro-profile information, the parameter k of grain surface _sembodied the texture materials stiffness characteristics.

The general micro-profile height H only obtained with scanning of domestic technique obtains the objective factor acting force of virtual texture power, and formula is:

the present invention has considered the rigidity information of people's grain surface material in touching the texture process on inferior basis, and the force that capable haptic apparatus is fed back spend more can the rediscover texture, adds parameter k on original formula _sas grain surface material stiffness coefficient, consider that soft, the hard Factors on Human of texture materials touches the impact of texture perception, has increased the validity of texture force touch perception.

2, proposed one and considered the virtual texture haptic modeling algorithm of subjective factor to the texture sensation influence, subjective factor Calculation of the force formula is:

this formula has embodied the impact of people's subjective perception custom on the texture perception, parameter a _ver(F _p, v), for the present invention is based on any pressing force that actual measurement calculates and the vertical direction accekeration under sweep velocity, embodied the impact on the texture perception of different perception customs and perception velocities, k _aembodied the weight relationship of subjective factor acting force and objective factor acting force, made the perception of virtual texture power more meet people's actual impression.

At present, the domestic research there is no specifically people's subjective factor in perception.The foreign study worker has the investigation of pair subjective factor and certain analysis is arranged, but does not also use the specific algorithm of vertical direction acting force research subjective factor to reproducing texture force touch.

The accompanying drawing explanation

The logical procedure diagram that Fig. 1 is the inventive method;

The experiment schematic diagram that Fig. 2 is the inventive method;

Fig. 3 is the bilinear interpolation binary look-up table schematic diagram adopted in the inventive method.

Embodiment

Below in conjunction with embodiment and accompanying drawing, technical solution of the present invention is described in detail.

With reference to Fig. 1, texture force measuring method in haptic feedback of the present invention: the hand controller of steering force tactile sense reproduction equipment is controlled virtual probe convergence virtual texture surface, carry out collision detection in virtual texture power model, the bump power output of front power haptic apparatus of virtual probe and grain surface is 0, after virtual probe and the generation collision of virtual texture surface, calculate respectively the vertical direction acting force of fictitious force

with the horizontal direction acting force

vertical last, by hand controller by virtual texture power

output.

With reference to Fig. 2, experiment schematic diagram of the present invention: when virtual probe contact grain surface, produce contact force

the acting force that is vertical direction by distribution of contact forces

acting force with horizontal direction

be convenient to analytical calculation.

The 80 order sand paper of take are example, set forth the specific embodiment of the invention process:

(1) use three-dimensional optical surface profiler KS-1100 to measure the grain surface profile, obtain grain surface micro-profile height H;

(2) the texture detecting pen is streaked in 80 order coated abrasive surface, choosing respectively pressing force F is 0.2N, 0.5N, 0.8N, 1.1N, 1.4N, sweep velocity v is 50mm/s, 100mm/s, 150mm/s, 200mm/s, utilizes the acceleration transducer in detecting pen to measure respectively corresponding vertical direction acceleration a _i.Can obtain the mean square deviation of every group of pressing force F and the corresponding vertical direction acceleration of sweep velocity v

wherein, the number that N is every group of vertical direction accekeration, use correlativity and regression analysis, obtains vertical direction acceleration mean square deviation a _rms(F _p, v) with pressing force F _pand the funtcional relationship of sweep velocity v: a _rms(F _p, v)=A * F _p+ B * v, wherein, A, B are constant coefficient.It is specific as follows that correlation analysis and regression are analyzed:

Correlation analysis is the statistical method a kind of commonly used of degree in close relations between the different variablees of research, the statistic of linear degree of correlation between variable of can describing of calculating according to sample number is called sample correlation coefficient, usually with Pearson simple correlation coefficient r, mean, the computing formula of r is:

x wherein _i, y _ifor two Variables Sequences of correlation analysis,

be respectively x _i, y _imean value, n is array x _i, y _iquantity.Vertical direction acceleration mean square deviation a to having measured respectively _rmsabout pressing force value F _pand sweep velocity v carries out correlation analysis, calculate correlation coefficient r, when | r|<0.3, for faint relevant; When 0.3≤| during r|<0.5, be lower correlation; When 0.5≤| during r|<0.8, for moderate relevant; When 0.8≤| r|<1 is height correlation.

Confirming vertical direction acceleration mean square deviation a _rmswith pressing force value F _pand, under the condition of sweep velocity v linear dependence, adopting multiple linear regression analysis to determine the mathematical relation of correlative, the mathematical formulae of describing this respective amount relation is called multiple linear regression equations.In multiple linear regression analysis, the estimation of regression coefficient adopts least square method.If multiple linear regression equations is: a _rms=β ₀* F _p+ β ₁* v, establish multiple linear sample regression equation and be:

wherein,

for β ₀, β ₁estimated value, residual sum of squares (RSS) is expressed as

according to the principle of minimizing in differentio-integral equation, known SSE certainly exists minimal value, in order to make SSE, obtains minimum value, and SSE is to β ₀, β ₁partial derivative should equal zero, that is:

$\left\{\begin{array}{c}\frac{\&PartialD;\mathrm{SSE}}{\&PartialD;{\mathrm{\&beta;}}_0}=-2\mathrm{\&Sigma;}(a_{\mathrm{rms}}-{\hat{a}}_{\mathrm{rms}})F_P=0\\ \frac{\&PartialD;\mathrm{SSE}}{\&PartialD;{\mathrm{\&beta;}}_1}=-2\mathrm{\&Sigma;}(a_{\mathrm{rms}}-{\hat{a}}_{\mathrm{rms}})v=0\end{array}\right.$

Can obtain β by solution formula ₀, β ₁estimated value

?

be constant factor A, B;

(3) virtual texture power vertical direction objective factor acting force modeling, formula is as follows:

${\stackrel{\&RightArrow;}{F}}_{\mathrm{obj}}=k_1\&times;k_s\&times;H\&times;\stackrel{\&RightArrow;}{n};$

Wherein, k _sa constant describing the texture materials stiffness coefficient, when H is virtual probe perception texture and the corresponding grain surface profile of the contact point height of grain surface, k ₁constant factor,

it is the vertical direction vector of unit length;

Constant k _sbe numerically equal to the linear coefficient of vertical direction acceleration mean square deviation and pressing force, be a _rms(F _p, v)=A * F _pconstant coefficient A in+B * v.Constant factor k ₁computing formula be

wherein, F _maxfor the maximum power output of actual forces feedback device, constant c ₁value is the arbitrary numerical value in 0.6-0.8;

(4) virtual texture power vertical direction subjective factor acting force modeling, formula is as follows:

${\stackrel{\&RightArrow;}{F}}_{\mathrm{sub}}=k_a\&times;a_{\mathrm{ver}}(F_p,v)\&times;\stackrel{\&RightArrow;}{n};$

Wherein, a _ver(F _p, v) be any pressing force size F in perception _pwith the vertical direction acceleration under any perception velocities v, k _afor degree of will speed up signal a _ver(F _p, v) be converted into force signal

the constant factor computing formula be: wherein, determine the objective factor acting force with the subjective factor acting force

the constant c of weight ratio ₂value is the arbitrary numerical value in 0.1-0.4, F _objfor the vertical direction acceleration of measured objective factor acting force under any pressing force and exploration speed; it is the vertical direction vector of unit length;

Any pressing force size F in the said sensed process _pwith the vertical direction acceleration a under any perception velocities v _ver(F _p, computation process v) has been used the method for linear predictive coding, specific as follows:

The normal acceleration value a (k) (k=1,2..., N) obtained for actual measurement, the number that N is one group of acceleration information under specific pressing force and sweep velocity, establish vertical direction acceleration signal predicted value and be

the exponent number that wherein p is linear prediction filter, the present invention gets p=10,

for coefficient of linear prediction wave filter, by the Levinson-Durbin Algorithm for Solving, obtained, the prediction residual of linear prediction filter

predicated error sequence E _r=e (1), e (2) ..., e (k) ..., e (N) }, in order to utilize white noise signal to synthesize stationary random signal, can set up a white noise sequence equated with its power spectrum density according to the predicated error sequence, the power spectrum density of white noise sequence is obtain with to pressing force F _i(i ∈ 1 ..., 5}) with sweep velocity v _j(j ∈ 1 ..., 4}) corresponding parameter

set up with pressing force F _p, the sweep velocity v binary look-up table that is coordinate, as shown in Figure 3, experiment measuring pressing force value F _i(i ∈ 1 ..., 5}) with scanning constant velocity amplitude v _j(j ∈ 1 ..., 4}) corresponding point are defined as Q _ij=(F _i, v _j), this respective value is horizontal ordinate F _iordinate v _junder condition after the linear prediction of vertical direction acceleration signal wherein,

the corresponding pressing force F of difference _i(i ∈ 1 ..., 5}) sweep velocity v _j(j ∈ 1 ..., the 4}) coefficient of linear prediction wave filter of lower vertical direction acceleration signal

with Power Spectrum of White Noise density σ ², defined function according to the bilinear interpolation theory, the pressing force when the perception texture and sweep velocity are no more than binary look-up table bounds F ₁≤ F≤F ₅and v ₁≤ v≤v ₄the time, to be evaluated numerical value weighted mean by contiguous four net points obtains, and computing formula is:

$\left\{\begin{array}{c}g\left(R_1\right)=\frac{F_{i+1}-F}{F_{i+1}-F_i}g\left(Q_{\mathrm{ij}}\right)+\frac{F-F_i}{F_{i+1}-F_i}g\left(Q_{(i+1)j}\right)\\ g\left(R_2\right)=\frac{F_{i+1}-F}{F_{i+1}-F_i}g\left(Q_{i(j+1)}\right)+\frac{F-F_i}{F_{i+1}-F_i}g\left(Q_{(i+1)(j+1)}\right)\\ g\left(P\right)=({\stackrel{\&RightArrow;}{h}}_{\mathrm{new}},{\mathrm{\&sigma;}}_{\mathrm{new}}^2)=\frac{v_{j+1}-v}{v_{j+1}-v_j}g\left(R_1\right)+\frac{v-v_j}{v_{j+1}-v_j}g\left(R_2\right)\end{array}\right.,i\&Element;\{1,...,4\},j\&Element;\{1,...,3\}$

When the pressing force when the perception texture and sweep velocity surpass binary look-up table bounds, adopt boundary speed or terminal pressure value to solve current perception state g (P) as sweep velocity value or the force value of this point, its computing formula is as follows:

$\left\{\begin{array}{cc}({\stackrel{\&RightArrow;}{h}}_{\mathrm{new}},{\mathrm{\&sigma;}}_{\mathrm{new}}^2)=g\left(P\right)=\frac{v_{j+1}-v}{v_{j+1}-v_j}g\left(Q_{1j}\right)+\frac{v-v_j}{v_{j+1}-v_j}g\left(Q_{1(j+1)}\right)& F<F_1\\ ({\stackrel{\&RightArrow;}{h}}_{\mathrm{new}},{\mathrm{\&alpha;}}_{\mathrm{new}}^2)=g\left(P\right)=\frac{v_{j+1}-v}{v_{j+1}-v_j}g\left(Q_{5j}\right)+\frac{v-v_j}{v_{j+1}-v_j}g\left(Q_{5(j+1)}\right)& F>F_5\\ ({\stackrel{\&RightArrow;}{h}}_{\mathrm{new}},{\mathrm{\&sigma;}}_{\mathrm{new}}^2)=g\left(P\right)=\frac{F_{i+1}-F}{F_{i+1}-F_i}g\left(Q_{i1}\right)+\frac{F-F_i}{F_{i+1}-F_i}g\left(Q_{(i+1)1}\right)& v<v_1\\ ({\stackrel{\&RightArrow;}{h}}_{\mathrm{new}},{\mathrm{\&alpha;}}_{\mathrm{new}}^2)=g\left(P\right)=\frac{F_{i+1}-F}{F_{i+1}-F_i}g\left(Q_{i5}\right)+\frac{F-F_i}{F_{i+1}-F_i}g\left(Q_{(i+1)5}\right)& v>v_4\end{array}\right.$

Obtain the correlation parameter of required point

utilize power spectrum density

generate white noise sequence { w (k) }, last, utilize coefficient of linear prediction wave filter

with white noise sequence { w (k) } realizes that signal is synthetic, composite formula is: $a_g\left(k\right)=w\left(k\right)+\underset{l=1}{\overset{p}{\mathrm{\&Sigma;}}}{t}_l{a}_g(k-1)=w\left(k\right)+{\stackrel{\&RightArrow;}{h}}^T{\stackrel{\&RightArrow;}{a}}_g(k-1),$ A _g(k) be the accekeration under desired any pressing force and sweep velocity.

Claims (1)

1. the texture force measuring method in a haptic feedback, is characterized in that, the method comprises the following steps:

In virtual texture power model, utilize the virtual probe that the lever of haptic feedback equipment is controlled in model to streak on the dummy object surface, whether detect virtual probe and dummy object comes in contact simultaneously, and whether relative motion arranged, if virtual probe and dummy object come in contact or without relative motion, virtual texture power

be output as 0, otherwise, virtual texture power calculated according to the following formula

and output:

${\stackrel{\&RightArrow;}{F}}_{\mathrm{con}}={\stackrel{\&RightArrow;}{F}}_{\mathrm{ver}}+{\stackrel{\&RightArrow;}{F}}_{\mathrm{hor}};$

Wherein, for the vertical direction acting force of virtual texture power,

for the horizontal direction acting force of virtual texture power, ${\stackrel{\&RightArrow;}{F}}_{\mathrm{ver}}={\stackrel{\&RightArrow;}{F}}_{\mathrm{obj}}+{\stackrel{\&RightArrow;}{F}}_{\mathrm{sub}};{\stackrel{\&RightArrow;}{F}}_{\mathrm{hor}}=\stackrel{\&RightArrow;}{f},$ Wherein, for the objective factor acting force, for the subjective factor acting force,

the suffered horizontal direction friction force of virtual probe during for relative motion;

Described objective factor acting force calculate according to the following formula:

${\stackrel{\&RightArrow;}{F}}_{\mathrm{obj}}=k_1\&times;k_s\&times;H\&times;\stackrel{\&RightArrow;}{n};$

Wherein, k _sa constant describing the texture materials stiffness coefficient, when H is virtual probe perception texture and the corresponding grain surface profile of the contact point height of grain surface, k ₁constant factor,

it is the vertical direction vector of unit length;

Constant k _sbe numerically equal to the linear coefficient A of vertical direction acceleration mean square deviation and pressing force, the computing formula of vertical direction acceleration mean square deviation is:

wherein, N is the group number of measured vertical direction acceleration, a _ibe the vertical direction acceleration information by the actual measurement of texture detecting pen, in order to obtain the linear coefficient A of vertical direction acceleration mean square deviation and pressing force, use correlation analysis and regretional analysis to calculate with pressing force F _p, sweep velocity v is independent variable, with vertical direction acceleration mean square deviation a _rmsfunctional relation for dependent variable: a _rms(F _p, v)=A * F _p+ B * v, wherein, A is vertical direction acceleration mean square deviation a _rmswith pressing force F _plinear coefficient, B is vertical direction acceleration mean square deviation a _rmswith the linear coefficient of sweep velocity v, F _pfor pressing force in the actual measurement process, v is sweep velocity in the actual measurement process; Constant factor k ₁computing formula be

wherein, F _maxfor the maximum power output of actual forces feedback device, constant c ₁value is the arbitrary numerical value in 0.6-0.8;

Described subjective factor acting force

calculate according to the following formula:

${\stackrel{\&RightArrow;}{F}}_{\mathrm{sub}}=k_a\&times;a_{\mathrm{ver}}(F_p,v)\&times;\stackrel{\&RightArrow;}{n};$

Wherein, a _ver(F _p, v) be pressing force size F arbitrarily in the perception of using the method for linear predictive coding and bilinear interpolation to obtain _pwith the vertical direction acceleration under any perception velocities v, k _afor degree of will speed up signal a _ver(F _p, v) be converted into force signal

constant factor, computing formula is:

Wherein, determine the objective factor acting force

with the subjective factor acting force

the constant c of weight ratio ₂value is the arbitrary numerical value in 0.1-0.4, F _objfor the vertical direction acceleration of measured objective factor acting force under any pressing force and exploration speed;

it is the vertical direction vector of unit length;

Described horizontal direction frictional resistance

calculate according to the following formula:

$\stackrel{\&RightArrow;}{f}=\mathrm{\&mu;}\&times;\left|F_{\mathrm{ver}}\right|\&times;\stackrel{\&RightArrow;}{t}$

Wherein, μ is the coefficient of sliding friction of virtual probe when the virtual texture surface sliding, F _verfor texture power vertical direction acting force,

for the horizontal direction vector of unit length.

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