Patent Publication Number: US-10330498-B2

Title: Sensor arrangement for the contactless sensing of angles of rotation on a rotating part

Description:
This application is a 35 U.S.C. § 371 National Stage Application of PCT/EP2015/072370, filed on Sep. 29, 2015, which claims the benefit of priority to Serial No. DE 10 2014 220 454.2, filed on Oct. 9, 2014 in Germany, the disclosures of which are incorporated herein by reference in their entirety. 
     The present disclosure is directed to a sensor arrangement for the contactless sensing of angles of rotation according to definition of the species in independent patent claim  1 . 
     Various inductive rotational angle sensors are known from the related art. The coupling between an exciter coil and one or multiple sensor coils is largely influenced by the rotational angle position of a coupling element (target). The evaluation of coupling factors requires complex electronics. The shape of the rotational angle signal profile is generally highly dependent on the geometry and arrangement of the sensor coils and targets used. 
     DE 197 38 836 A1 describes, for example, an inductive angle sensor including a stator element, a rotor element, and an evaluation circuit. The stator element has an exciter coil which is subjected to a periodic AC voltage, and multiple receiving coils. The rotor element specifies the intensity of the inductive coupling between the exciter coil and the receiving coils, as a function of its angular position relative to the stator element. The evaluation circuit determines the angular position of the rotor element relative to the stator element, from the voltage signals induced in the receiving coils. 
     SUMMARY 
     In contrast, the sensor arrangement according to the present disclosure for the contactless sensing of angles of rotation having the features of independent patent claim  1  has the advantage that the measurement of an angle of rotation is possible by determining the inductance of a plurality of individual coils, preferably three or six circularly arranged coils. Advantageously, the evaluation and control unit generates evaluation signals having a signal profile which is very similar to a three-phase sinusoidal signal, so that the evaluation is possible using simple algorithms. The individual detection coils show a specific geometry. 
     A three-phase sinusoidal signal profile has the advantage that the angle of rotation may be deduced (Scott-T transformation) from the measured inductances of the individual detection coils using comparatively simple calculation specifications. Advantageously, the consideration of mechanical tolerances, for example, offset or tilt of the target, is implementable via the simple mathematical relationships. Sine, cosine, and/or tangent functions, as well as their inverse functions, may be processed relatively simply using a microcontroller which is part of the evaluation and control unit. 
     The three-phase signal profile is achieved via a circular arrangement of three or six coils. Depending on the number of metal surfaces of the target, a periodicity of 90° or 180° is obtained. Thus, a periodicity of 90° may be implemented if the target has four metal surfaces. If the target has only two metal surfaces, a periodicity of 180° may be implemented. 
     In order to obtain a sinusoidal signal, the geometry of the coil is correspondingly adjusted. Embodiments of the sensor arrangement according to the present disclosure include a coil arrangement in which the spacing between the conducting paths of the individual windings of the detection coils or coil sections is adjusted in such a way that sweeping the metal surfaces of the target causes the inductance of the coil to change in such a way that a sinusoidal profile of the rotational angle signal results. 
     Exemplary embodiments of the present disclosure provide a sensor arrangement for the contactless sensing of angles of rotation on a rotating part which is coupled with a disk-shaped target which has at least one metal surface, and which generates at least one piece of information for ascertaining the instantaneous angle of rotation of the rotating part, in connection with a coil arrangement which has at least one flat detection coil. According to the present disclosure, the coil arrangement includes three flat detection coils which are uniformly distributed on the circumference of a circle, and the rotating target includes at least two metal surfaces which influence the inductances of the flat detection coils due to eddy current effects, as a function of the degree of overlap, wherein an evaluation and control unit generates essentially sinusoidal evaluation signals which represent the changes in inductance in the detection coils, and evaluates them for calculating the angle of rotation. 
     Advantageous improvements on the sensor arrangement for the contactless sensing of angles of rotation specified in the independent claim  1  are possible via the measures and refinements listed in the dependent claims. 
     It is particularly advantageous that each of the flat detection coils may have two coil sections having an opposite winding sense, which may be arranged opposite one another on the circumference of the circle. Due to the opposite winding sense of the two coil sections, advantageous EMC characteristics result with respect to emission and the coupling-in of interference signals. In addition, the opposite arrangement of the coil sections on a circular circumference results in low sensitivity with respect to assembly tolerances. 
     In one advantageous embodiment of the sensor arrangement according to the present disclosure, the flat coil sections may be designed as uniform circle segments and/or annular segments having a predefined opening angle. In the case of the use of three flat detection coils, the opening angle of the flat detection coils preferably has a value in the range of 100° to 120° in each case. In the case of the use of three distributed detection coils, the opening angle of the flat coil sections has a value in the range of 50° to 60° in each case. 
     In an additional advantageous embodiment of the sensor arrangement according to the present disclosure, a spacing between two conducting path sections, which extend in a circular arc shape, of the individual detection coil or coil section, may be chosen to be as small as possible, and a spacing between two radially extending conducting path sections of the individual detection coil or coil section may be chosen in such a way that the radially extending conducting path sections are distributed as uniformly as possible over the available surface of the individual detection coil or coil section. As a result, a sufficiently high inductance for the individual detection coils or coil sections may be achieved, whereby the detection and evaluation of the changes in inductance may be facilitated in an advantageous manner. 
     In an additional advantageous embodiment of the sensor arrangement according to the present disclosure, the metal surfaces may be designed as uniform circle segments and/or annular segments having a predefined opening angle. The opening angle of the metal surfaces may have a value in the range from 50° to 120° in each case, as a function of the number of metal surfaces. 
     To generate three phase-shifted essentially sinusoidal evaluation signals, the associated target may, for example, have four metal surfaces which are arranged uniformly distributed on the circumference of a circle, each having an opening angle of 60°. The evaluation and control unit generates three phase-shifted, essentially sinusoidal evaluation signals from the changes in inductance in the three detection coils effected by the rotational movement of the target, and evaluates them for calculating the angle of rotation in an unambiguous range of 90°. In order to increase the unambiguous range to 180°, the target may have two metal surfaces arranged opposite one another on the circumference of a circle, each having an opening angle of 120°, wherein the evaluation and control unit generates three phase-shifted, essentially sinusoidal evaluation signals from the changes in inductance in the three detection coils effected by the rotational movement of the target, and evaluates them for calculating the angle of rotation in an unambiguous range of 180°. 
     Exemplary embodiments of the present disclosure are illustrated in the drawings and are described in greater detail in the description below. In the drawings, identical reference numerals refer to components or elements which carry out identical or similar functions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a schematic top view of a first exemplary embodiment of a sensor arrangement according to the present disclosure for the contactless sensing of angles of rotation. 
         FIG. 2  shows a schematic top view of a first exemplary embodiment of a coil arrangement for the sensor arrangement according to the present disclosure from  FIG. 1 . 
         FIG. 3  shows a schematic top view of a detection coil for the coil arrangement from  FIG. 2 . 
         FIG. 4  shows a characteristic curve diagram of the evaluation signals generated by the sensor arrangement according to the present disclosure for the contactless sensing of angles of rotation from  FIG. 1 . 
         FIG. 5  shows a schematic top view of a second exemplary embodiment of a sensor arrangement according to the present disclosure for the contactless sensing of angles of rotation. 
         FIG. 6  shows a schematic top view of a second exemplary embodiment of a coil arrangement for the sensor arrangement according to the present disclosure from  FIG. 5 . 
         FIG. 7  shows a schematic top view of a detection coil for the coil arrangement from  FIG. 6 . 
         FIG. 8  shows a characteristic curve diagram of the evaluation signals generated by the sensor arrangement according to the present disclosure for the contactless sensing of angles of rotation from  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION 
     As is apparent from  FIGS. 1 to 8 , the depicted exemplary embodiment of a sensor arrangement  1 ,  1 A according to the present disclosure for the contactless sensing of angles of rotation on a rotating part each include a target  20 ,  20 A coupled with the rotating part, which has an annular disk-shaped base body  22 ,  22 A with at least one metal surface  24 ,  24 A, and a coil arrangement  40 ,  40 A with at least one flat detection coil  42 ,  44 ,  46 ,  42 A,  44 A,  46 A, which is arranged on a round printed circuit board  30 ,  30 A. In connection with the coil arrangement  40 ,  40 A, the target  20 ,  20 A generates at least one piece of information for ascertaining the instantaneous angle of rotation of the rotating part. According to the present disclosure, the coil arrangement  40 ,  40 A includes three flat detection coils  42 ,  44 ,  46 ,  42 A,  44 A,  46 A which are uniformly distributed on the circumference of a circle, and the rotating target  20 ,  20 A comprises at least two metal surfaces  24 ,  24 A which influence the inductances of the flat detection coils  42 ,  44 ,  46 ,  42 A,  44 A,  46 A due to eddy current effects, as a function of the degree of overlap. In this case, an evaluation and control unit  10  generates essentially sinusoidal evaluation signals K 1 , K 2 , K 3 , K 1 A, K 2 A, K 3 A, which represent the changes in inductance in the detection coils  42 ,  44 ,  46 ,  42 A,  44 A,  46 A, and evaluates them for calculating the angle of rotation. The evaluation signals K 1 , K 2 , K 3 , K 1 A, K 2 A, K 3 A are described in greater detail below with reference to  FIGS. 3 and 8 . 
     As is furthermore apparent from  FIGS. 1 to 8 , the coil arrangement  40 ,  40 A in the depicted embodiment is arranged on a round printed circuit board  30 ,  30 A and is electrically connected to an evaluation and control unit  10 . Of course, the printed circuit board  30 ,  30 A does not have to be round; the printed circuit board  30 ,  30 A may also have another suitable shape. The annular disk-shaped base body  22 ,  22 A of the target  20 ,  20 A, which is depicted as transparent in the drawings, is arranged at a predefined constant axial distance above or below the printed circuit board  30 ,  30 A. In the depicted exemplary embodiments, the rotating part, which is not depicted in detail, may be a shaft which, having sufficient lateral play, is routed through the circular opening in the printed circuit board  30 ,  30 A, and is connected to the base body  22 ,  22 A of the target  20 ,  20 A in a rotationally fixed manner. 
     As is furthermore apparent from  FIGS. 1 to 3 , the first exemplary embodiment of the coil arrangement  40  includes three detection coils  42 ,  44 ,  46  which are arranged in a distributed manner over the circumference of the circular coil arrangement  40 . As is furthermore apparent from  FIG. 1 , the target  20  of the depicted first exemplary embodiment of the sensor arrangement  1  according to the present disclosure includes two annular segment-shaped metal surfaces  24 , each having an opening angle with a value in the range of 100° to 120°. As is apparent in particular from  FIG. 2 , the flat detection coils  42 ,  44 ,  46  are designed as uniform annular segments having a predefined opening angle which has a value in the range of 100° to 120°. 
     As is furthermore apparent from  FIG. 3 , conducting paths L having the thickness B, which form the respective winding of the associated detection coil  42 ,  44 ,  46 , of which a first detection coil  42  is depicted by way of example, have circular arc-shaped conducting path sections L B  and radially extending conducting path sections L R . A spacing d K , which the conducting path sections L R , which extend in a circular arc shape, have with respect to one another, is preferably chosen to be as small as possible in order to accommodate as many coil windings N as possible on the available surface of the detection coil  42 ,  44 ,  46 . The maximum number N of coil windings may be approximately calculated using equation (1). 
     
       
         
           
             
               
                 
                   N 
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     Here, r a  denotes an outer radius, r i  denotes an inner radius of the corresponding detection coil  42 ,  44 ,  46 , r m  denotes a radial expansion of a free surface in the center of the corresponding coil  42 ,  44 ,  46 , and B denotes the conducting path width. Both the minimum conducting path width B and the minimum spacing d K  between two circular arc-shaped conducting path sections L B  are, for example, 125 μm. The values for the remaining variables are, for example, r a =8.35 mm, r i =4 mm, and r m =0.75 mm. Using the above formula, a winding count of N=7.7 results for the depicted exemplary embodiment. 
     The spacing d R  of the radially extending conducting path sections L R  is chosen in such a way that the radially extending conducting path sections L R  are distributed as uniformly as possible over the entire available surface of the corresponding detection coil  42 ,  44 ,  46 . The suitable conducting path spacing d R  may be approximately calculated using equation (2). 
     
       
         
           
             
               
                 
                   
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     In the depicted first exemplary embodiment, the spacing d R  is, for example, 480 μm. A length X representing the perpendicular spacing between the center of the coil and the outermost radial conducting path sections L R  may be determined using equation (3). 
     
       
         
           
             
               
                 
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     Here, θ denotes the angle formed by the radially extending conducting path sections L R  of the left and right coil halves; α denotes the opening angle of the circular conducting path sections L R . In the depicted first exemplary embodiment of the coil arrangement  40 , θ=120° and α=100°. 
     As is apparent from the associated characteristic curve diagram according to  FIG. 4 , the three generated phase-shifted evaluation signals K 1 , K 2 , K 3  run in an approximately sinusoidal manner, wherein the evaluation and control unit  10  generates a first evaluation signal K 1  by evaluating the first detection coil  42 , generates a second evaluation signal K 2  by evaluating the second detection coil  44 , and generates a third evaluation signal K 3  by evaluating the third detection coil  46 .  FIG. 1  shows, by way of example, the position of the target  20  at an angle of rotation of 0°, where the determination results by definition. The opening angles of the detection coils  42 ,  44 ,  46  are each 100°, and the opening angles of the metal surfaces  24  of the target  20  are each 120°. Due to the use of only two metal surfaces  24 , the rotational angle measuring range is 180°. In the depicted characteristic curve diagram according to  FIG. 4 , a resonant frequency is plotted along the perpendicular axis, which changes due to the change in inductance in the respective detection coil  42 ,  44 ,  46 . Of course, other suitable measurable physical variables may also be used in order to detect and depict a change in inductance in the respective detection coil  42 ,  44 ,  46 . 
     As is furthermore apparent from  FIGS. 5 to 7 , the second exemplary embodiment of the coil arrangement  40 A includes three detection coils  42 A,  44 A,  46 A which are arranged in a distributed manner over the circumference of the circular coil arrangement  40 A, each being divided into two coil sections  42 . 1 A,  42 . 2 A,  44 . 1 A,  44 . 2 A,  46 . 1 A,  46 . 2 A. Thus, a total of six coil sections  42 . 1 A,  42 . 2 A,  44 . 1 A,  44 . 2 A,  46 . 1 A,  46 . 2 A are uniformly arranged in a distributed manner over the circumference of the circular coil arrangement  40 A. The two coil sections  42 . 1 A,  42 . 2 A,  44 . 1 A,  44 . 2 A,  46 . 1 A,  46 . 2 A of the respective detection coils  42 A,  44 A,  46 A are each arranged in a distributed manner over the circumference of the circular coil arrangement  40 A in such a way that lateral positional tolerances are compensated for, to a first approximation. In the depicted second exemplary embodiment, the two coil sections  42 . 1 A,  42 . 2 A,  44 . 1 A,  44 . 2 A,  46 . 1 A,  46 . 2 A of the respective detection coils  42 A,  44 A,  46 A are arranged opposite one another on the circumference of the circular coil arrangement  40 A. The winding sense of the two coil sections  42 . 1 A,  42 . 2 A,  44 . 1 A,  44 . 2 A,  46 . 1 A,  46 . 2 A of the respective detection coils  42 A,  44 A,  46 A is opposite, so that the magnetic field at a distance of approximately three coil diameters is very small, and the coupling-in of interference signals may be compensated for. 
     As is apparent in particular from  FIG. 6 , the flat coil sections  42 . 1 A,  42 . 2 A,  44 . 1 A,  44 . 2 A,  46 . 1 A,  46 . 2 A are each designed as uniform annular segments having a predefined opening angle of 50°. In the depicted exemplary embodiments, a first detection coil  42 A is made up of the two flat coil sections  42 . 1 A and  42 . 2 A; a second detection coil  44 A is made up of the two coil sections  44 . 1 A and  44 . 2 A, and a third detection coil  46 A is made up of the two flat coil sections  46 . 1 A and  46 . 2 A. 
     As is furthermore apparent from  FIG. 5 , the target  20 A of the depicted second exemplary embodiment sensor arrangement  1 A according to the present disclosure for the contactless sensing of angles of rotation on a rotating part includes four annular segment-shaped metal surfaces  24 A having an opening angle of 60°.  FIG. 5  shows, by way of example, the position of the targets  20 A at an angle of rotation of 0°, wherein the determination takes place by definition. It is apparent that a shift of the center point of the target  20 A in the positive y-direction (orientation corresponding to the page surface) results in an enlargement of the overlap of the second coil section  46 . 2 A of the third detection coil  46 A and in a reduction in the overlap of the first coil section  46 . 1 A of the third detection coil  46 A. The same relationship applies to the coil sections  44 . 1 A and  44 . 2 A of the second detection coil  44 A. In this position of the target  20 A, the relationship does not apply to the coil sections  42 . 1 A and  42 . 2 A of the first detection coil  42 A, since there is generally no effect on these coil sections  42 . 1 A,  42 . 2 A due to a slight (&lt;5% of the diameter) shift of the target  20 A in the y-direction, due to a larger design of the target  20 A in the radial direction. 
     It is possible to measure the inductance of the six coil sections  42 . 1 A and  42 . 2 A,  44 . 1 A and  44 . 2 A, and  46 . 1 A and  46 . 2 A separately, and to carry out the correction corresponding to the following specification, where L m  represents the calculated average value of the inductance of the coil section, which results from the measured inductances of the coil sections  42 . 1 A,  42 . 2 A,  44 . 1 A,  44 . 2 A,  46 . 1 A,  46 . 2 A of the respective detection coil  42 A,  44 A,  46 A and which may be determined according to equation (4). Here, L1 and L2 each represent the measured inductance of the corresponding coil sections  42 . 1 A,  42 . 2 A,  44 . 1 A,  44 . 2 A,  46 . 1 A,  46 . 2 A.
 
 L   m =( L 1+ L 2)/2  (4)
 
     The calculation may take place in the evaluation and control unit  10 . In the depicted second exemplary embodiment, the two coil sections  42 . 1 A,  42 . 2 A,  44 . 1 A,  44 . 2 A,  46 . 1 A,  46 . 2 A of the detection coils  42 A,  44 A,  46 A are electrically connected in series. Since the coupling factors between the coil sections  42 . 1 A,  42 . 2 A,  44 . 1 A,  44 . 2 A,  46 . 1 A,  46 . 2 A are relatively small, with k&lt;0.02, the inductances are additive. The formation of the average thus takes place in a virtually “analog” manner, without computing effort. In addition, the number of connections between the coil arrangement  40 A and the evaluation and control unit  10  is reduced. To reduce the susceptibility to interference and to reduce the field emissions, each of the coil sections  42 . 1 A,  42 . 2 A,  44 . 1 A,  44 . 2 A,  46 . 1 A,  46 . 2 A is wound in the opposite sense, as already indicated above. As a result, the far-field magnetic field strength is reduced. Assuming a homogeneous interference field, equal voltages having a different sign in each case are induced in the two coil sections  42 . 1 A,  42 . 2 A,  44 . 1 A,  44 . 2 A,  46 . 1 A,  46 . 2 A. Due to the series connection, the two voltages ideally offset each other at zero. 
     As is furthermore apparent from  FIG. 7 , conducting paths L having the thickness B, which form the respective winding of the coil sections  42 . 1 A,  42 . 2 A,  44 . 1 A,  44 . 2 A,  46 . 1 A,  46 . 2 A of the detection coils  42 A,  44 A,  46 A, of which a first coil section  42 . 1 A of the first detection coil  42 A is depicted by way of example, have circular arc-shaped conducting path sections L B  and radially extending conducting path sections L R , similarly to the first exemplary embodiment. A spacing d K , which the conducting path sections L B , which extend in a circular arc shape, have with respect to one another, is preferably chosen to be as small as possible in order to as many coil windings N as possible on the available surface of the coil section  42 . 1 A,  42 . 2 A,  44 . 1 A,  44 . 2 A,  46 . 1 A,  46 . 2 A. The maximum number N of coil windings may be approximately calculated using equation (1). Similarly to the first exemplary embodiment, both the minimum conducting path width B and the minimum spacing d K  between two circular arc-shaped conducting path sections L B  are, for example, 125 μm. The values for the remaining variables are, for example, r a =8.35 mm, r i =4 mm, and r m =0.75 mm. Similarly to the first exemplary embodiment, a winding count of N=7.7 results for the coil sections  42 . 1 A,  42 . 2 A,  44 . 1 A,  44 . 2 A,  46 . 1 A,  46 . 2 A. 
     Similarly to the first exemplary embodiment, the spacing d R  of the radially extending conducting path sections L R  is chosen in such a way that the radial radially extending conducting path sections L R  are distributed as uniformly as possible over the entire available surface of the corresponding coil section  42 . 1 A,  42 . 2 A,  44 . 1 A,  44 . 2 A,  46 . 1 A,  46 . 2 A. The suitable conducting path spacing d R  may also be approximately calculated using equation (2). In the depicted second exemplary embodiment, the spacing d R  is, for example, 230 μm. In addition, in the depicted second exemplary embodiment of the coil arrangement  40 A, θ=60° and α=50°. 
     As is apparent from the associated characteristic curve diagram according to  FIG. 8 , the three generated phase-shifted evaluation signals K 1 A, K 2 A, K 3 A run in an approximately sinusoidal manner, similarly to the first exemplary embodiment, wherein the evaluation and control unit  10  generates a first evaluation signal K 1 A by evaluating the first detection coil  42 A having the coil sections  42 . 1 A and  42 . 2 A, generates a second evaluation signal K 2 A by evaluating the second detection coil  44 A having the coil sections  44 . 1 A and  44 . 2 A, and generates a third evaluation signal K 3 A by evaluating the third detection coil  46 A having the coil sections  46 . 1 A and  46 . 2 A. In addition, a symmetry exists between the coil sections  42 . 1 A and  42 . 2 A,  44 . 1 A and  44 . 2 A, and  46 . 1 A and  46 . 2 A. In the case of an exactly central position of the target  20 A with respect to the coil arrangement  40 A, there is no difference between the respective partners and the evaluation signals K 1 A, K 2 A, K 3 A. Due to the use of four metal surfaces  24 A, the rotational angle measuring range is 90°. Similarly to the characteristic curve diagram according to  FIG. 4 , in the characteristic curve diagram depicted in  FIG. 8 , a resonant frequency is plotted along the perpendicular axis, which changes due to the change in inductance in the respective detection coil  42 A,  44 A,  46 A. Of course, other suitable measurable physical variables may also be used in order to detect and depict a change in inductance in the respective detection coil  42 A,  44 A,  46 A.