CN102054122B - Haptic texture rendering method based on practical measurement - Google Patents

Abstract

The invention discloses a haptic texture rendering method based on practical measurement, which is characterized in that after an operational handle of haptic texture display equipment collides with the surface of a virtual texture, resultant force of normal textural force, normal binding force and tangential friction is taken as contact force to be output to an operator. The normal textural force is obtained by measuring pressure which really scratches the surface of the texture, a mechanical arm which applies constant force and is provided with a pressure sensor at the bottom is used to scratch the surface of a textural material at a constant speed and collect data meanwhile, and after error item correction, smoothness, voltage value conversion, mechanical arm constant force value subtraction of the data, the data are converted into the normal textural force; the modeling of the normal binding force adopts a spring damping model; and the modeling of the tangential friction synthesizes a static friction stage and a sliding friction stage, the modeling at the static friction stage adopts the product of maximal static friction and a sine function, a coefficient of kinetic friction at the sliding friction stage is obtained by calculating the normal textural force reflecting the concave-convex degree of the texture, and the naturalness of the texture rendering is improved.

Description

Power haptic rendering method based on the texture of actual measurement

Technical field

The present invention relates to the power haptic rendering method of texture, specifically proposed a kind of expression of the texture power based on true measurement.

Background technology

Along with the development of virtual reality technology, power haptic rendering technology is day by day remarkable for the importance of pseudo operation.Texture is the comprehensive description of the characteristic such as the microcosmos geometric shape, roughness of body surface, and the power haptic rendering research of texture is very important.The power haptic rendering of texture is that the texture information of body surface is fed back to the operator by haptic feedback equipment, can make the truly physical attribute of perception texture of operator, thereby make the operator obtain strong feeling of immersion and the sense of reality, this is the final goal that texture force touch is expressed.

At present, mainly according to the height profile feature of grain surface, the contact force computation model when foundation contacts with grain surface reproduces texture power to the operator by haptic feedback equipment the power haptic rendering of texture, thereby reproduces the concave-convex sense of texture.The method for building up of the power haptic model of texture has three kinds usually: (1) extracts grain surface feature contour feature from image, sets up texture force touch and expresses model; (2) based on geometrical constraint and physical model, set up texture force touch and express model; (3) by the concavo-convex profile of actual measurement grain surface, produce fictitious force touch texture power mapping model.

Express model based on the power touch texture that image is processed, this is the focus in present reproducing texture force touch field.This model need to extract the feature of grain surface from image, not only image processing algorithm is had relatively high expectations, and is also very high to the accuracy requirement of image itself.But the quality owing to image itself can not guarantee usually, can not reflect truly texture information by image calculation grain surface height out.

The interaction of power that the texture force touch of setting up based on geometrical constraint has been expressed model realization between two polygon models.The power touch texture of Physical modeling based is expressed model and is mainly comprised sinusoidal model, probabilistic model etc.Sinusoidal model is modeled as the sinusoidal signal that the roughness with article surface vein changes with the texture contact force, and body surface is more coarse, and the amplitude of cyclical signal is just larger, and texture is finer and closely woven, and then the frequency of periodic signal is higher.The method to a certain extent can the reflected well texture characteristic, but the texture kind that deterministic models can be expressed is limited, only can make force feeling that obvious discrimination is arranged, but lacks the sense of reality, can not texture tactility that is virtually reality like reality.Research on stochastic model mainly concentrates on the random descriptive statistics, and statistical method comprises auto-correlation, marginal density, feature histogram and random field etc.The contact force that different textures produces has different numerical characteristics, and by changing the value of numerical characteristic, the roughness of superficial makings can be changed.But only can express the roughness of texture based on the power haptic rendering of probabilistic model, can not reproduce the real concavo-convex and tendency that grain surface exists.

The sensor or the instrument that are used for the measurement superficial makings mainly are divided into two kinds: a kind of is contactless, without any contact, obtains surface topography information by optical technology between object and the surveying instrument.Such as the light probe interferometric method, adopt very thin focused light probe incident measured surface, the height change of body surface causes reference light and the variation of measuring the light optical path difference, by the phase bit comparison, can obtain the profile on surface.But measuring method is had relatively high expectations to the cleanliness of measured surface, and dust is larger on its measurement result impact.Another kind is contact, and probe contacts with body surface, measures the outline data of grain surface, again the geometric profile data is converted to texture power.The most widely used contact type measurement instrument is the contact pin type contourgraph, and they generally adopt adamas probe scanning measured surface.The people such as Vasudevan propose with the probe of PHANToM hand controller the grain surface profile to be explored, and measure the displacement of vertical direction probe.By profile information being converted to after the texture power, using various power haptic models and texture is expressed carry out the power Haptic Rendering.The method that also has is the texture power when measuring staff and initiatively slipping over grain surface, at this moment needs to reject the staff subjectivity and applies power to the impact of measurement result.

Summary of the invention

The invention provides and a kind ofly can improve the power haptic rendering method based on the texture of actual measurement that texture power is expressed authenticity.

A kind of power haptic rendering method of the texture based on actual measurement is characterized in that:

The lever convergence virtual texture of steering force tactile sense reproduction equipment surface, the power output of establishing before bumping with grain surface is 0, after bumping with grain surface, produces normal direction texture power

The normal direction binding force And tangential friction force

At last, with normal direction texture power The normal direction binding force

And tangential friction force

Make a concerted effort as contact force

And with this contact force

As power output;

Described normal direction texture power

Generated by following methods:

Step 1 is chosen real texture materials;

Step 2 is installed in pressure transducer the bottom of mechanical arm;

Step 3 is at the uniform velocity mobile on the texture materials surface with the mechanical arm of pressure transducer, and mechanical arm applies constant force F _In, making pressure transducer and texture materials Surface Contact, and obtain the data of sampling with sampling apparatus, the sampling rate of data is 1000Hz, i.e. time resolution ax/t ₀Be 0.001s, record mechanical arm tangential movement speed v _sWith displacement S, sampling number

Step 4 is carried out the data processing with the magnitude of voltage of measured pressure transducer, comprising:

(1) data pre-service:

If the arbitrary voltage sample value in the N that surveys sampled point is less than voltage reference value U ₀, then with voltage reference value U ₀Replace described less than voltage reference value U ₀Arbitrary voltage sample value, at this moment, the voltage sample value of N sampled point is u ₀₁, u ₀₂... u _0N, adopt five-spot triple smoothing that the voltage sample value is carried out smoothing processing, concrete formula is:

$\left\{\begin{array}{c}{u}_1=\frac{1}{70}[69u_{01}+4(u_{02}+u_{04})-6u_{03}-u_{05}]\\ u_2=\frac{1}{35}[2(u_{01}+u_{05})+27u_{02}+12u_{03}-8u_{04}]\\ u_i=\frac{1}{35}[-3(u_{0i-2}+u_{0i+2})+12(u_{0i-1}+u_{0i+1})+17u_{0i}]\\ u_{N-1}=\frac{1}{35}[2(u_{0N-4}+u_{0N})-8u_{0N-3}+12u_{0N-2}+27u_{0N-1}]\\ u_N=\frac{1}{70}[-u_{0N-4}+4(u_{0N-3}+u_{0N-1})-6u_{0N-2}+69u_{0N}]\end{array}\right.$

In the formula, u ₁, u ₂... u _NBe the voltage sample value after level and smooth, i=3,4 ... N-2;

(2) with the voltage sample value u after level and smooth ₁, u ₂... u _NBe converted to force value F ₁, F ₂... F _N, according to the circuit theory conversion formula be J=1,2 ... N, wherein, U ₀Be voltage reference value, L is transducer sensitivity, and G is the constant that is determined by circuit;

(3) with force value F _jDeduct the constant force value F that mechanical arm applies _In, obtain reflecting the concavo-convex different force value of grain surface, i.e. normal direction texture power

Normal direction texture power

Sequence table be shown

J=1,2 ... N, formula is:

$f_{\mathrm{texture}}^{\→}\left(j\right)=F_j-F_{\mathrm{in}},j=\mathrm{1,2},...N$

Step 5 is with texture power

In virtual scene coordinate system Oxyz, express, be expressed as

(1) initialization haptic feedback equipment and virtual scene; Virtual scene coordinate system Oxyz is set, suppose that the coordinate of the point of impingement under virtual scene space coordinates Oxyz is (x, y, z), { 0≤x≤X, 0≤y≤Y, z=Z} are the texture materials surface in zone in the coordinate system, zone { 0≤x≤X, 0≤y≤Y, z＞Z} are that texture materials is outside, zone { 0≤x≤X, 0≤y≤Y, z＜Z} is that texture materials is inner, and X, Y represent respectively texture region at the boundary position coordinate of x axle, y axle, and X＞0, Y＞0, Z represents the position coordinates of texture plane on the z axle;

(2) with N-1 plane

With area of space z≤Z} average mark is slit into N zonule for 0≤x≤X, 0≤y≤Y, in arbitrary zonule, texture power

All be a fixed value, along the z direction of principal axis, concrete formula is:

$f_{\mathrm{texture}}^{\&RightArrow;}(x,y,z)=f_{\mathrm{texture}}^{\&RightArrow;}\left(j\right),$ When $(x,y,z)\&Element;\{\frac{(j-1)X}{N}<x\&le;\frac{\mathrm{jX}}{N},0\&le;y\&le;Y,z\&le;Z|j=\mathrm{1,2},...N\}$

Described normal direction binding force

Generated by following methods:

The normal direction binding force

Be modeled as the spring damping model

Along the z direction of principal axis, concrete formula is:

$f_{\mathrm{constraint}}^{\&RightArrow;}(x,y,z)=k*|z-Z|+b*(-\frac{\mathrm{dz}}{\mathrm{dt}}),z\&le;Z;$

K*|z-Z| is the spring deformation item, k is stiffness coefficient, expression texture materials surface collided and the extruding situation under deformation extent, relevant with the attribute on texture materials surface, the k span is 0-1 (N/mm), and k is 1 (N/mm) when object is perfect rigidity, and k was 0 when object was full flexible, Z is the position coordinates of texture plane on the z axle, | z-Z| is the paracentesis depth of Z-direction;

Be damping term, For virtual probe along the axial instantaneous velocity of z, specific formula for calculation is

Δ t is the renewal rate of haptic feedback equipment, the viscous damping coefficient of b for being directly proportional with the energy consumption of texture materials surface deformation, the b span is 0.1-0.5, b is larger, the more difficult generation deformation in texture materials surface, the b value is 0.5 when object is perfect rigidity, and the b value was 0.1 when object was full flexible;

Described tangential friction force

Generated by following methods:

Tangential friction force Direction and virtual probe in relative motion or the relative motion trend opposite direction of X-Y plane, the computing formula of friction force under the virtual scene coordinate system

For:

$f_{\mathrm{friction}}^{\&RightArrow;}(x,y,z)=\left\{\begin{array}{c}\mathrm{\&mu;}(x,y,z)F_N(x,y,z),v\&le;-\left|v_r\right|\\ f_{\mathrm{ms}}\sin (-\frac{\mathrm{\&pi;}}{2\left|v_r\right|}v)={\mathrm{\&mu;}}_0(x,y,z)F_N(x,y,z)\sin (-\frac{\mathrm{\&pi;}}{2\left|v_r\right|}v),v<\left|v_r\right|\\ -\mathrm{\&mu;}(x,y,z)F_N(x,y,z),v\&GreaterEqual;\left|v_r\right|\end{array}\right.$

$=\left\{\begin{array}{c}\mathrm{\&mu;}(x,y,z)(f_{\mathrm{texture}}^{\&RightArrow;}(x,y,z)+f_{\mathrm{constraint}}^{\&RightArrow;}(x,y,z)),v\&le;-\left|v_r\right|\\ {\mathrm{\&mu;}}_0(x,y,z)(f_{\mathrm{texture}}^{\&RightArrow;}(x,y,z)+f_{\mathrm{constraint}}^{\&RightArrow;}(x,y,z))\sin (-\frac{\mathrm{\&pi;}}{2\left|v_r\right|}v),v<\left|v_r\right|\\ -\mathrm{\&mu;}(x,y,z)(f_{\mathrm{texture}}^{\&RightArrow;}(x,y,z)+f_{\mathrm{constraint}}^{\&RightArrow;}(x,y,z)),v\&GreaterEqual;\left|v_r\right|\end{array}\right.$

In the formula v be virtual probe in the translational speed of X-Y plane, computing formula is v _rBe virtual probe in the speed limit of X-Y plane, when v＜| v _r| the time, being approximate relative static conditions, friction force is modeled as stiction

f _Ms=μ ₀(x, y, z) F _N(x, y, z) is maximum static friction force, μ ₀(x, y, z) is the coefficient of static friction of the point of impingement, F _N(x, y, z) represents normal pressure, i.e. normal direction texture power

With the normal direction binding force

Vector and; When movement speed v 〉=| v _r| or v≤-| v _r|, friction force is modeled as force of sliding friction, F _N(x, y, z) represents normal pressure, is normal direction texture power

With the normal direction binding force Vector and, μ (x, y, z) is dynamic friction factor, and is relevant with the degree of roughness of the material of surface of contact and surface of contact, the expression formula of μ (x, y, z) is:

μ (x, y, z)=ρ r (x, y, z), wherein ρ is the coefficient of roughness of texture materials, and r (x, y, z) is the local roughness coefficient of the point of impingement, and is relevant with the local concavo-convex degree of this point of impingement, and the calculating of r (x, y, z) is obtained by following formula:

C wherein _nBe flexible strategy, value and distance Be inversely proportional to, and

The value of q is generally 2 or 3; Coefficient of static friction μ in the model ₀(x, y, z) is more than or equal to kinetic friction coefficient μ (x, y, z).

Advantage of the present invention

1, the pressure of perception texture is measured the surface characteristics that can embody texture, concavo-convex such as texture, the data that gather are processed through data, namely correct mistakes, level and smooth, voltage force value conversion, be converted to virtual texture power after deducting mechanical arm constant force value, because virtual texture power and real-texture surface contact force change consistent characteristics, the texture power that therefore will extract from true measurement environment is used in the modeling of power and exports with haptic feedback equipment is the reliable means of realization real-texture expression;

2, the measuring method science of pressure is simple, use the end constant in grain surface slip and the mechanical arm application of force evenly with the mechanical arm of pressure transducer, both got rid of the impact of staff application of force inequality for measured pressure value, reached again the correspondence in sampling time and space, and be convenient to analyze;

3, contact force model is modeled as the vector addition model of normal direction texture power, normal direction binding force, tangential friction force, this meets the general characteristic that staff touches the perception texture, normal direction texture power has embodied the rough tendency of texture, the normal direction binding force has embodied the material properties of object, tangential friction force has embodied the degree of roughness of article surface vein, and these all are the requisite key elements that realizes the texture truly expressed;

4, the binding force model is the spring damping model, embodied article surface vein collided and the extruding situation under deformation extent, and damping term is directly proportional with the movement velocity of normal direction, reflected that the movement velocity of normal direction when the actual touch grain surface is on the impact of the size variation of contact force, normal velocity is larger, the contact force of experiencing is larger, and the bump impression is more obvious;

The trend of power changes when 5, simulating more really the perception texture for the model of the power that makes foundation, the combined action of stiction and force of sliding friction has been considered in the modeling of friction force, when relatively static between virtual probe and the grain surface but when relative motion trend is arranged, friction force is modeled as nonlinear stiction, it is the product of maximum static friction force and sine function, increase gradually when movement velocity but also do not reach speed in limited time, stiction increases with the increase of speed, until after speed reached speed limit, friction force just was converted into force of sliding friction;

6, the kinetic friction coefficient in the force of sliding friction is not only relevant with the material coefficient of roughness on texture materials surface, also relevant with the local roughness coefficient, the local roughness coefficient is by obtaining apart from square process weighted sum of the point of impingement apart from the difference of the measurement point that does not wait and point of impingement texture power around the point of impingement, the degree of fluctuation that has reflected texture, meet the information that staff slips over the power of feeding back of grain surface, improved the sense of reality that texture is expressed.

Description of drawings

Fig. 1 is system chart of the present invention;

Fig. 2 is normal direction texture power of the present invention

Product process figure;

Fig. 3 is experiment schematic diagram of the present invention;

Fig. 4 is contact force of the present invention

Model;

Fig. 5 is virtual scene coordinate system schematic diagram of the present invention;

Fig. 6 is the collision response schematic diagram under the virtual scene coordinate of the present invention;

Specific embodiments

Be described in further detail below in conjunction with the enforcement of accompanying drawing to technical scheme:

With reference to Fig. 1, a kind of power haptic rendering method of the texture based on actual measurement is characterized in that:

The lever convergence virtual texture of steering force tactile sense reproduction equipment surface, the power output of establishing before bumping with grain surface is 0, after bumping with grain surface, produces normal direction texture power

The normal direction binding force

And tangential friction force

At last, with normal direction texture power

The normal direction binding force

And tangential friction force

Make a concerted effort as contact force

And with this contact force

Be power output, with reference to Fig. 4, namely

$f_{\mathrm{contact}}^{\&RightArrow;}=f_{\mathrm{texture}}^{\&RightArrow;}+f_{\mathrm{constraint}}^{\&RightArrow;}+f_{\mathrm{friction}}^{\&RightArrow;};$

With reference to Fig. 2, described normal direction texture power Generated by following methods:

Step 1 is chosen real texture materials: Art Stone;

Step 2 is installed in pressure transducer the bottom of mechanical arm;

Step 3 makes with the mechanical arm of pressure transducer at the uniform velocity mobile at grain surface, and as shown in Figure 3: mechanical arm applies constant force F _In=1N makes pressure transducer and texture materials Surface Contact, and obtains the data of sampling with sampling apparatus, and the sampling rate of data is 1000Hz, i.e. time resolution ax/t ₀Be 0.001s, record mechanical arm tangential movement speed v _s=10mm/s and displacement S=100mm, sampling number

Step 4 is carried out the data processing with the magnitude of voltage of measured pressure transducer, comprising:

(1) data pre-service:

If the arbitrary voltage sample value in the N=10001 that surveys sampled point is less than voltage reference value U ₀, then with voltage reference value U ₀Replace described less than voltage reference value U ₀Arbitrary voltage sample value, U in this circuit ₀=2.42V, at this moment, the voltage sample value of N sampled point is u ₀₁, u ₀₂... u _0N, adopt five-spot triple smoothing that the voltage sample value is carried out smoothing processing, concrete formula is:

$\left\{\begin{array}{c}{u}_1=\frac{1}{70}[69u_{01}+4(u_{02}+u_{04})-6u_{03}-u_{05}]\\ u_2=\frac{1}{35}[2(u_{01}+u_{05})+27u_{02}+12u_{03}-8u_{04}]\\ u_i=\frac{1}{35}[-3(u_{0i-2}+u_{0i+2})+12(u_{0i-1}+u_{0i+1})+17u_{0i}]\\ u_{N-1}=\frac{1}{35}[2(u_{0N-4}+u_{0N})-8u_{0N-3}+12u_{0N-2}+27u_{0N-1}]\\ u_N=\frac{1}{70}[-u_{0N-4}+4(u_{0N-3}+u_{0N-1})-6u_{0N-2}+69u_{0N}]\end{array}\right.$

In the formula, u ₁, u ₂... u _NBe the voltage sample value after level and smooth, i=3,4 ... N-2;

(2) with the voltage sample value u after level and smooth ₁, u ₂... u _NBe converted to force value F ₁, F ₂... F _N, according to the circuit theory conversion formula be J=1,2 ... N, wherein, U ₀=2.42V, L=0.12mv/g, G=17.467;

(3) with force value F _jDeduct the constant force value F that mechanical arm applies _In, obtain reflecting the concavo-convex different force value of grain surface, i.e. normal direction texture power Normal direction texture power Sequence table be shown

J=1,2 ... N, formula is:

$f_{\mathrm{texture}}^{\&RightArrow;}\left(j\right)=F_j-F_{\mathrm{in}},j=\mathrm{1,2},...N$

If texture power

Less than 0, then show the contact point depression, if texture power

Greater than 0, expression contact point projection;

Step 5 is with texture power

In virtual scene coordinate system 0xyz, express, be expressed as

(1) initialization haptic feedback equipment and virtual scene; With reference to Fig. 5, virtual scene coordinate system 0xyz is set, suppose that the coordinate of the point of impingement under virtual scene space coordinates 0xyz is (x, y, z), { 0≤x≤X of the zone in the coordinate system, 0≤y≤Y, z=Z} are the texture materials surface, zone { 0≤x≤X, 0≤y≤Y, z＞Z} are that texture materials is outside, zone { 0≤x≤X, 0≤y≤Y, z＜Z} are that texture materials is inner, wherein get X=200, Y=200, Z=0;

(2) with N-1 plane With area of space 0≤x≤X, 0≤y≤Y, z≤Z} are divided into N zonule, in arbitrary zonule, texture power All be a fixed value, along the z direction of principal axis, concrete formula is:

$f_{\mathrm{texture}}^{\&RightArrow;}(x,y,z)=f_{\mathrm{texture}}^{\&RightArrow;}\left(j\right),$ When $(x,y,z)\&Element;\{\frac{(j-1)X}{N}<x\&le;\frac{\mathrm{jX}}{N},0\&le;y\&le;Y,z\&le;Z|j=\mathrm{1,2},...N\}$

With reference to Fig. 6, described normal direction binding force

Generated by following methods:

Binding force

Be modeled as the spring damping model

Along the z direction of principal axis:

$f_{\mathrm{constraint}}^{\&RightArrow;}(x,y,z)=k*|z-Z|+b*(-\frac{\mathrm{dz}}{\mathrm{dt}}),z\&le;Z;$

K*|z-Z| is the spring deformation item, and k is stiffness coefficient, expression texture materials surface collided and the extruding situation under deformation extent, relevant with the attribute on texture materials surface, it is the position coordinates of texture plane on the z axle that k gets 0.8, Z, | z-Z| is the paracentesis depth of Z-direction;

Be damping term,

For virtual probe along the axial instantaneous velocity of z, specific formula for calculation is Δ t is the renewal rate of haptic feedback equipment, the viscous damping coefficient of b for being directly proportional with the energy consumption of texture materials surface deformation, and the b span is 0.1-0.5, b is larger, the more difficult generation deformation in texture materials surface, b gets 0.4;

Described tangential friction force

Generated by following methods:

Tangential friction force

Direction and virtual probe in relative motion or the relative motion trend opposite direction of X-Y plane, the computing formula of friction force under the virtual scene coordinate system For:

$f_{\mathrm{friction}}^{\&RightArrow;}(x,y,z)=\left\{\begin{array}{c}\mathrm{\&mu;}(x,y,z)F_N(x,y,z),v\&le;-\left|v_r\right|\\ f_{\mathrm{ms}}\sin (-\frac{\mathrm{\&pi;}}{2\left|v_r\right|}v)={\mathrm{\&mu;}}_0(x,y,z)F_N(x,y,z)\sin (-\frac{\mathrm{\&pi;}}{2\left|v_r\right|}v),v<\left|v_r\right|\\ -\mathrm{\&mu;}(x,y,z)F_N(x,y,z),v\&GreaterEqual;\left|v_r\right|\end{array}\right.$

$=\left\{\begin{array}{c}\mathrm{\&mu;}(x,y,z)(f_{\mathrm{texture}}^{\&RightArrow;}(x,y,z)+f_{\mathrm{constraint}}^{\&RightArrow;}(x,y,z)),v\&le;-\left|v_r\right|\\ {\mathrm{\&mu;}}_0(x,y,z)(f_{\mathrm{texture}}^{\&RightArrow;}(x,y,z)+f_{\mathrm{constraint}}^{\&RightArrow;}(x,y,z))\sin (-\frac{\mathrm{\&pi;}}{2\left|v_r\right|}v),v<\left|v_r\right|\\ -\mathrm{\&mu;}(x,y,z)(f_{\mathrm{texture}}^{\&RightArrow;}(x,y,z)+f_{\mathrm{constraint}}^{\&RightArrow;}(x,y,z)),v\&GreaterEqual;\left|v_r\right|\end{array}\right.$

V be virtual probe in the translational speed of X-Y plane, computing formula is

v _rRule of thumb be worth under the virtual scene coordinate system and get 0.072/s, be equivalent to 8mm/s, when v＜| v _r| the time, being approximate relative static conditions, friction force is modeled as stiction

f _Ms=μ ₀(x, y, z) F _N(x, y, z) is maximum static friction force, μ ₀(x, y, z) is the coefficient of static friction of the point of impingement, F _N(x, y, z) represents normal pressure, i.e. normal direction texture power

With the normal direction binding force

Vector and; When movement speed v 〉=| v _r| or v≤-| v _r|, friction force is modeled as force of sliding friction, F _N(x, y, z) represents normal pressure, and μ (x, y, z) is dynamic friction factor, and be relevant with the degree of roughness of the material of surface of contact and surface of contact, and the expression formula of μ (x, y, z) is:

μ (x, y, z)=ρ r (x, y, z), wherein ρ is the coefficient of roughness of texture materials, ρ=0.4, and r (x, y, z) is the local roughness coefficient of contact point, relevant with the local concavo-convex degree of this contact point, the calculating of r (x, y, z) is obtained by following formula:

$r(x,y,z)=\underset{n\&NotEqual;0}{\overset{q}{\underset{n=-q}{\mathrm{\&Sigma;}}}}{c}_n{|F_{\mathrm{texture}}^{\&RightArrow;}(x-\frac{\mathrm{nX}}{N},y,z)-F_{\mathrm{texture}}^{\&RightArrow;}(x,y,z)|}^2$

Work as q=2,

Get coefficient of static friction μ in the model ₀(x, y, z) equals kinetic friction coefficient μ (x, y, z);

The work space of the lever of the moving area of virtual probe and haptic feedback equipment is set up the spatial mappings relation in the virtual scene coordinate system, wherein, lever positional information (the Px of haptic feedback equipment output, Py, Pz) obtained by the canonical function dhdGetPosition () among the haptic feedback equipment standard function library API, (x in the virtual scene coordinate system, y, z) by the lever coordinate figure (Px of haptic feedback equipment, Py, Pz) get through the coordinate zooming and panning, concrete ratio variation relation is as follows:

x＝9*Px，y＝9*Py，z＝5*Pz-5

At last, normal direction texture power in the virtual scene

The normal direction binding force

And tangential friction force

Make a concerted effort by the output of the canonical function dhdSetForce () among the haptic feedback equipment standard function library API.

Claims (1)

1. power haptic rendering method based on the texture of actual measurement is characterized in that:

The lever convergence virtual texture of steering force tactile sense reproduction equipment surface, the power output of establishing before bumping with grain surface is 0, after bumping with grain surface, produces normal direction texture power

The normal direction binding force And tangential friction force

At last, with normal direction texture power

The normal direction binding force

And tangential friction force

Make a concerted effort as contact force

And with this contact force

As power output;

Described normal direction texture power

Generated by following methods:

Step 1: choose real texture materials;

Step 2: the bottom that pressure transducer is installed in mechanical arm;

Step 3: the mechanical arm with pressure transducer is at the uniform velocity mobile on the texture materials surface, and mechanical arm applies constant force F _In, making pressure transducer and texture materials Surface Contact, and obtain the data of sampling with sampling apparatus, the sampling rate of data is 1000Hz, i.e. time resolution ax/t ₀Be 0.001s, record mechanical arm tangential movement speed v _sWith displacement S, sampling number $N=\frac{S}{v_s*{\mathrm{\&Delta;t}}_0}+1;$

Step 4: the magnitude of voltage of measured pressure transducer is carried out the data processing, comprising:

(1) data pre-service:

If the arbitrary voltage sample value in the N that surveys sampled point is less than voltage reference value U ₀, then with voltage reference value U ₀Replace described less than voltage reference value U ₀Arbitrary voltage sample value, at this moment, the voltage sample value of N sampled point is u ₀₁, u ₀₂... u _0N, adopt five-spot triple smoothing that the voltage sample value is carried out smoothing processing, concrete formula is:

$\left\{\begin{array}{c}{u}_1=\frac{1}{70}[{69u}_{01}+4(u_{02}+u_{04})-{6u}_{03}-u_{05}]\\ u_2=\frac{1}{35}[2(u_{01}+u_{05})+{27u}_{02}+{12u}_{03}-{8u}_{04}]\\ u_i=\frac{1}{35}[-3(u_{0i-2}+u_{0i+2})+12(u_{0i-1}+u_{0i+1})+{17u}_{0i}]\\ u_{N-1}=\frac{1}{35}[2(u_{0N-4}+u_{0N})-{8u}_{0N-3}+{12u}_{0N-2}+{27u}_{0N-1}]\\ u_N=\frac{1}{70}[{-u}_{0N-4}+4(u_{0N-3}+u_{0N-1})-{6u}_{0N-2}+{69u}_{0N}]\end{array}\right.$

In the formula, u ₁, u ₂... u _NBe the voltage sample value after level and smooth, i=3,4 ... N-2;

(2) with the voltage sample value u after level and smooth ₁, u ₂... u _NBe converted to force value F ₁, F ₂... F _N, according to the circuit theory conversion formula be J=1,2 ... N, wherein, U ₀Be voltage reference value, L is transducer sensitivity, and G is the constant that is determined by circuit;

(3) with force value F _jDeduct the constant force value F that mechanical arm applies _In, obtain reflecting the concavo-convex different force value of grain surface, i.e. normal direction texture power

Normal direction texture power

Sequence table be shown

J=1,2 ... N, formula is:

$f_{\mathrm{texture}}^{\&RightArrow;}\left(j\right)=F_j-F_{\mathrm{in}},j=\mathrm{1,2},...N$

Step 5: with texture power

In virtual scene coordinate system Oxyz, express, be expressed as

(1) initialization haptic feedback equipment and virtual scene; Virtual scene coordinate system Oxyz is set, suppose that the coordinate of the point of impingement under virtual scene space coordinates Oxyz is (x, y, z), { 0≤x≤X, 0≤y≤Y, z=Z} are the texture materials surface in zone in the coordinate system, zone { 0≤x≤X, 0≤y≤Y, z〉Z} is that texture materials is outside, zone { 0≤x≤X, 0≤y≤Y, z＜Z} is that texture materials is inner, and X, Y represent respectively texture region at the boundary position coordinate of x axle, y axle, and X〉0, Y〉0, Z represents the position coordinates of texture plane on the z axle;

(2) with N-1 plane $\{x=\frac{\mathrm{mX}}{N},0\&le;y\&le;Y,z\&le;Z|m=\mathrm{1,2},...,N-1\}$ With area of space z≤Z} average mark is slit into N zonule for 0≤x≤X, 0≤y≤Y, in arbitrary zonule, texture power

All be a fixed value, along the z direction of principal axis, concrete formula is:

$f_{\mathrm{texture}}^{\&RightArrow;}(x,y,z)=f_{\mathrm{texture}}^{\&RightArrow;}\left(j\right),$ When $(x,y,z)\&Element;\{\frac{(j-1)X}{N}<x\&le;\frac{\mathrm{jX}}{N},0\&le;y\&le;Y,z\&le;Z|j=\mathrm{1,2},...N\}$

Described normal direction binding force

Generated by following methods:

The normal direction binding force

Be modeled as the spring damping model

Along the z direction of principal axis, concrete formula is:

$f_{\mathrm{constraint}}^{\&RightArrow;}(x,y,z)=k*|z-Z|+b*(-\frac{\mathrm{dz}}{\mathrm{dt}}),z\&le;Z;$

K*|z-Z| is the power that the spring deformation item produces, k is stiffness coefficient, expression texture materials surface collided and the extruding situation under deformation extent, relevant with the attribute on texture materials surface, the k span is 0-1 (N/mm), and k is 1 (N/mm) when object is perfect rigidity, and k was 0 when object was full flexible, Z is the position coordinates of texture plane on the z axle, | z-Z| is the paracentesis depth of Z-direction;

Be damping term,

For virtual probe along the axial instantaneous velocity of z, specific formula for calculation is

Δ t is the renewal rate of haptic feedback equipment, the viscous damping coefficient of b for being directly proportional with the energy consumption of texture materials surface deformation, the b span is 0.1-0.5, b is larger, the more difficult generation deformation in texture materials surface, the b value is 0.5 when object is perfect rigidity, and the b value was 0.1 when object was full flexible;

Described tangential friction force

Generated by following methods:

Tangential friction force

Direction and virtual probe in relative motion or the relative motion trend opposite direction of X-Y plane, the computing formula of friction force under the virtual scene coordinate system

For:

$f_{\mathrm{friction}}^{\&RightArrow;}(x,y,z)=\left\{\begin{array}{c}\mathrm{\&mu;}(x,y,z)F_N(x,y,z),v\&le;-\left|v_r\right|\\ f_{\mathrm{ms}}\sin (-\frac{\mathrm{\&pi;}}{2\left|v_r\right|}v)={\mathrm{\&mu;}}_0(x,y,z)F_N(x,y,z)\sin (-\frac{\mathrm{\&pi;}}{2\left|v_r\right|}v),v<\left|v_r\right|\\ -\mathrm{\&mu;}(x,y,z)F_N(x,y,z),v\&GreaterEqual;\left|v_r\right|\end{array}\right.$

$\left\{\begin{array}{c}\mathrm{\&mu;}(x,y,z)(f_{\mathrm{texture}}^{\&RightArrow;}(x,y,z)+f_{\mathrm{constraint}}^{\&RightArrow;}(x,y,z)),v\&le;-\left|v_r\right|\\ {\mathrm{\&mu;}}_0(x,y,z)(f_{\mathrm{texture}}^{\&RightArrow;}(x,y,z)+f_{\mathrm{constraint}}^{\&RightArrow;}(x,y,z))\sin (-\frac{\mathrm{\&pi;}}{2\left|v_r\right|}v),v<\left|v_r\right|\\ -\mathrm{\&mu;}(x,y,z)(f_{\mathrm{texture}}^{\&RightArrow;}(x,y,z)+f_{\mathrm{constraint}}^{\&RightArrow;}(x,y,z)),v\&GreaterEqual;\left|v_r\right|\end{array}\right.$

In the formula v be virtual probe in the translational speed of X-Y plane, computing formula is $\left|v\right|=\frac{\sqrt{{[x\left(t\right)-x(t-\mathrm{\&Delta;t})]}^2+{[y\left(t\right)-y(t-\mathrm{\&Delta;t})]}^2}}{\mathrm{\&Delta;t}},$ v _rBe virtual probe in the speed limit of X-Y plane, when v＜| v _r| the time, being approximate relative static conditions, friction force is modeled as stiction

f _Ms=μ ₀(x, y, z) F _N(x, y, z) is maximum static friction force, μ ₀(x, y, z) is the coefficient of static friction of the point of impingement, F _N(x, y, z) represents normal pressure, i.e. normal direction texture power

With the normal direction binding force Vector and; When movement speed v 〉=| v _r| or v≤-| v _r|, friction force is modeled as force of sliding friction, F _N(x, y, z) represents normal pressure, is normal direction texture power

With the normal direction binding force

Vector and, μ (x, y, z) is dynamic friction factor, and is relevant with the degree of roughness of the material of surface of contact and surface of contact, the expression formula of μ (x, y, z) is:

μ (x, y, z)=ρ r (x, y, z), wherein ρ is the coefficient of roughness of texture materials, and r (x, y, z) is the local roughness coefficient of the point of impingement, and is relevant with the local concavo-convex degree of this point of impingement, and the calculating of r (x, y, z) is obtained by following formula:

$r(x,y,z)=\underset{n\&NotEqual;0}{\overset{q}{\underset{n=-q}{\mathrm{\&Sigma;}}}}{c}_n{|f_{\mathrm{texture}}^{\&RightArrow;}(x-\frac{\mathrm{nX}}{N},y,z)-f_{\mathrm{texture}}^{\&RightArrow;}(x,y,z)|}^2,$ C wherein _nBe flexible strategy, value and distance

Be inversely proportional to, and

Value be generally 2 or 3; Coefficient of static friction μ in the model ₀(x, y, z) is more than or equal to kinetic friction coefficient μ (x, y, z).

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