Method for measuring a torque applied to a magnetoelastic body

Abstract

A method for measuring stress applied to a magnetoelastic body, simultaneously detecting a potential external magnetic field affecting a magnetoelastic sensor and allocating a non-stress related influence affected by the field on the body, including applying at least two opposite magnetic zones on the body, providing at least one sensor including at least one first (1) and second (2) channel having at least two axially aligned coils each, arranged adjacent to the magnetized zone of the body, both channels having different sensitivity relative to the field, setting-up channel 1 as a common mode rejection channel and channel 2 as a common mode acceptance channel, reading the magnetized zones when stress is applied to the body, measuring the stress by channel 1 leading to an opposite sensitive direction, and detecting the impact of the field to the magnetized zones by channel 2 leading to an identical sensitive direction.

Claims

1. A method for measuring a stress applied to a magneto-elastic body (6) while simultaneously detecting an external magnetic field (19, 20) affecting the magneto-elastic body (6), wherein the method allocates non-stress related influence affected by the external magnetic field (19,20) to the measured stress by utilizing a magneto-elastic sensor (18), the method comprising the steps of: providing the magnet-elastic sensor (18) with at least two magnetic zones (3,7) of opposite magnetic orientation to each other on the magneto-elastic body (6), and providing magnet-elastic sensor (18) with at least one first channel (1) and at least one second channel (2), wherein the at least one first channel (1) and the at least one second channel (2) each comprise at least two coils (8,9,8′,9′) with both coils axially aligned, and with each of the coils arranged adjacent to the magnetized zone (3,7) of the magneto-elastic body (6), and the at least one first channel (1) and the at least one second channel (2) have a different sensitivity; configuring the at least one first channel (1) as a common mode rejection channel; configuring the at least one second channel (2) as a common mode acceptance channel; measuring a stress applied to the magnetized zones (3, 7) of the magneto-elastic body (6) by the at least one first channel (1) by reading said magnetized zones (3,7) with the respective at least two coil (8, 9, 8′, 9′) of the first channel (1) in a direction opposite to a center tap (CT) of the at least one first channel (1); detecting the impact of the external magnetic field (19, 20) by reading said magnetized zones (3,7) with the respective at least two coil (8, 9, 8′, 9′) of the at least one second channel (2) in a direction toward the center tap (CT) of the at least one first channel (1); and utilizing the magnetic zones (3, 7) of the magneto-elastic body (6) configured as a dual-band system.

2. A method for measuring a stress applied to a magnetoelastic body (6) while simultaneously detecting an external magnetic field (19, 20) affecting the magnetoelastic body (6), wherein the method allocates non-stress related influence affected by the external magnetic field (19,20) to the measured stress by utilizing a magneto-elastic sensor (18), the method comprising the steps of: providing the magnet-elastic sensor (18) with at least two magnetic zones (3,7) of opposite magnetic orientation to each other on the magnetoelastic body (6), and providing magnet-elastic sensor (18) with at least one first channel (1) and at least one second channel (2), wherein the at least one first channel (1) and the at least one second channel (2) each comprise at least two coils (8,9,8′,9′) with both coils axially aligned, and with each of the coils arranged adjacent to the magnetized zone (3,7) of the magnetoelastic body (6), and the at least one first channel (1) and the at least one second channel (2) have a different sensitivity; configuring the at least one first channel (1) as a common mode rejection channel; configuring the at least one second channel (2) as a common mode acceptance channel; measuring a stress applied to the magnetized zones (3, 7) of the magnetoelastic body (6) by the at least one first channel (1) by reading said magnetized zones (3,7) with the respective at least two coil (8, 9, 8′, 9′) of the first channel (1) in a direction opposite to a center tap (CT) of the at least one first channel (1); detecting the impact of the external magnetic field (19, 20) by reading said magnetized zones (3,7) with the respective at least two coil (8, 9, 8′, 9′) of the at least one second channel (2) in a direction toward the center tap (CT) of the at least one first channel (1); and wiring said coils (8, 9, 8′, 9′) in a diverging manner depending on their arrangement in common mode rejection or in common mode acceptance.

3. A magnetoelastic sensor (18) for measuring a stress applied to a magnetoelastic body (6) while simultaneously detecting an external magnetic field (19, 20) affecting a magnetoelastic sensor (18) and allocating a non-stress related influence affected by the external magnetic field (19, 20) to the measured stress, the magnetoelastic sensor (18) being adapted and configured to interact with the magnetoelastic body wherein the magnetoelastic body has at least two magnetic zones of opposite magnetic orientation to each other, the magnetoelastic sensor (18) comprising at least one first channel (1) and at least one second channel (2), the at least one first channel (1) and the at least one second channel (2) each comprising at least two coils (8,9,8′,9′), each of the two coils (8, 9, 8′, 9′) being axially aligned, the at least two coils (8,9,8′,9′) being adapted and configured to be arranged adjacent to the magnetized zone (3, 7) of the magnetoelastic body (6), the at least one channel (1) and the at least one second channel (2) each having a sensitivity, the sensitivity of the at least first channel (1) being different from the sensitivity of the at least one second channel (2), the at least one first channel (1) being set up as a common mode rejection channel, the at least one second channel (2) being set up as a common mode acceptance channel, the at least first channel (1) and the at least one second channel (2) being adapted and configured to read said magnetized zones of the magnetoelastic body (6) when stress is applied to the magnetoelastic body (6) and the external magnetic field affects the magnetoelastic sensor (18), the at least two coils (8, 9) of the at least one first channel (1) being adapted and configured to measure electric current flow in a direction opposite to the center tap (CT) of the at least one first channel (1), the at least one second channel (2) being adapted and configured to detect the external magnetic field (19, 20) by electric current flow in the at least two coils (8′,9′) of the at least one second channel 2 in the direction of the center tap (CT) of the at least one first channel (1), wherein said at least one first channel (1) and said at least one second channel (2) both comprise four coils (8, 9, 8′, 9′) each.

4. A magnetoelastic sensor (18) for measuring a stress applied to a magnetoelastic body (6) while simultaneously detecting an external magnetic field (19, 20) affecting a magnetoelastic sensor (18) and allocating a non-stress related influence affected by the external magnetic field (19, 20) to the measured stress, the magnetoelastic sensor (18) being adapted and configured to interact with the magnetoelastic body wherein the magnetoelastic body has at least two magnetic zones of opposite magnetic orientation to each other, the magnetoelastic sensor (18) comprising at least one first channel (1) and at least one second channel (2), the at least one first channel (1) and the at least one second channel (2) each comprising at least two coils (8,9,8′,9′), each of the two coils (8, 9, 8′, 9′) being axially aligned, the at least two coils (8,9,8′,9′) being adapted and configured to be arranged adjacent to the magnetized zone (3, 7) of the magnetoelastic body (6), the at least one channel (1) and the at least one second channel (2) each having a sensitivity, the sensitivity of the at least first channel (1) being different from the sensitivity of the at least one second channel (2), the at least one first channel (1) being set up as a common mode rejection channel, the at least one second channel (2) being set up as a common mode acceptance channel, the at least first channel (1) and the at least one second channel (2) being adapted and configured to read said magnetized zones of the magnetoelastic body (6) when stress is applied to the magnetoelastic body (6) and the external magnetic field affects the magnetoelastic sensor (18), the at least two coils (8, 9) of the at least one first channel (1) being adapted and configured to measure electric current flow in a direction opposite to the center tap (CT) of the at least one first channel (1), the at least one second channel (2) being adapted and configured to detect the external magnetic field (19, 20) by electric current flow in the at least two coils (8″,9″) of the at least one second channel 2 in the direction of the center tap (CT) of the at least one first channel (1), wherein said at least one first channel (1) and said at least one second channel (2) both having a different sensitivity relative to the external magnetic field (19, 20).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 a side view of a magnetoelastic body showing two magnetic zones according to the state of the art,

(2) FIG. 2a a schematic view of a channel 1 of a sensor with corresponding coils as well as connecting drives A and B with the center tap CT,

(3) FIG. 2b a schematic view of a channel 2 with corresponding coils as well as connecting drives A and B with the center tap CT,

(4) FIG. 3 shows the influence of the stress on both the channel 1 and the channel 2,

(5) FIG. 4 a diagram showing the influence of an external magnetic field to the channel 1 and the channel 2,

(6) FIG. 5a shows the magnetoelastic body of the sensor in a side view

(7) FIG. 5b shows the magnetoelastic body of the sensor in a front view,

(8) FIG. 6 a diagram showing a common mode rejection configuration for the sensor for measuring stress and

(9) FIG. 7 a diagram showing a common mode acceptance configuration for detecting a potential external magnetic field.

DETAILED DESCRIPTION

(10) FIG. 1 shows the magnetoelastic body 6 having two magnetic zones 3, 7.

(11) Each magnetic zone 3, 7 carries a direction of magnetization 4, 5.

(12) Said directions of magnetization 4, 5 are aligned oppositely to each other.

(13) The FIG. 2a shows a channel 1 of a magnetic field sensor 18 in the sense of the present invention. Said channel 1 measures the stress applied to the magnetoelastic body 6.

(14) According to the invention, the sensor 18 shown in FIG. 2a has at least one channel 1.

(15) The sensor 18 comprises at least said channel 1, which has at least two coils 8, 9. The sensor 18 shown in FIG. 2a further comprises at least drives A and B. Drives A and B represent the wiring connecting at least the corresponding coils 8, 9 with said tap (CT) of the channel 1. The sensor 18 also has means for measuring the current flowing from the Drives A and B to the center tap (CT) through the individual coil 8, 9 (not shown).

(16) The sensor 18 is referred to as a magnetic field sensor.

(17) In case, when stress is applied to the magnetoelastic body 6, the current flows in the coils 8, 9 of the channel 1 in opposite directions respectively, i.e. the channel 1 is set in the common mode rejection.

(18) The first channel 1 shown in the FIG. 2a is capable of measuring the stress applied to the magnetized zones 3, 7 (not shown) of the magnetoelastic body 6.

(19) In the FIG. 2a the channel 1 is set in common mode rejection.

(20) FIG. 2b shows a schematic view of said channel 2 with corresponding coils 8, 9 as well as connecting drives A and B, corresponding to the schematic view shown in FIG. 2a.

(21) However, in the FIG. 2b, channel 2 is shown. The second channel 2 is constructed in a way to detect the effect of the external magnetic field to the magnetoelastic sensor. Here, the current 12, 13, 14, 15 flows through said coils 8, 9 in an identical direction to the center tap (CT). This leads to an identical sensitive direction.

(22) In other words, when an external magnetic field is detected by channel 2, which affects the magnetoelastic sensor 18, the current flow 12, 13, 14, 15 in the coils 8, 9 of the channels 2 in the same directions respectively. Thus, the channel 2 is set in common mode acceptance.

(23) To flip the polarity of the coils 8, 9 to reverse the direction of the flow 12, 13, 14, 15 of the current within the coil 8, 9, in the FIGS. 2a and 2b the center tap CT needs to be adapted to the amended direction of the flow 12, 13, 14, 15 of the current. Thus, when the flow of the current in the relevant coil 8, 9 is reversed the measurement direction in the individual coil 8, 9 is reversed as well.

(24) Both the FIG. 3 and the FIG. 4 show a Cartesian coordinate system. On the Y-axis of both the FIG. 3 and the FIG. 4 the output voltage V is found.

(25) In the FIG. 3, the channel 1 shows the results of the measurement of the stress applied to the magnetoelastic body 6 relative to the increase of the current flowing through the coil 8, 9.

(26) As the channel 2 only measures the external magnetic field and does not show any sensitivity towards the stress, the channel 2 shown in the FIG. 3 runs in the X-axis.

(27) Contrary to each other, on the X-axis of the FIG. 4 the magnitude of the external magnetic field is shown, whereas values of the stress applied are depicted on the X-axis of the FIG. 3.

(28) In regard to the FIG. 4 the assumption is made that said external magnetic field is arranged at a given distance relative to the coils 8 and 9 of the channel 1 and the channel 2.

(29) FIG. 4 shows the varying values of magnitude of the external magnetic field. Said values being the results of said detecting channel 2. As the values of magnitude of the external magnetic field increase, measured by the channel 2 of the FIG. 4, the impact of the external magnetic field affecting the results of the channel 1 measuring the stress applied to the magnetoelastic body increases as well.

(30) Said results of channel 1 shown in the FIG. 4 represent the values of the external magnetic field sensed by the channel 1, measuring the stress, which is due to the sensitivity of the channel 1 relative to the external magnetic field. The results of the channel 1 shown in FIG. 4 represent the effect of the external magnetic field distorting the results of the channel 1, measuring the stress applied to the magnetoelastic body 6.

(31) The sensitivity of the channel 1 represents the impact of said external magnetic field on the results of the channel 1.

(32) The channel 2 shown in the FIG. 4 represent the values of the external magnetic field detected by the channel 2 as the voltage shown on the Y-axis increases.

(33) The FIG. 5 is a two-part presentation of the magnetoelastic body 6 with its magnetic zones 3, 7 and coils 8, 9 of said channels 1 and channel 2.

(34) On the left, FIG. 5 shows a side view 16 of said magnetoelastic body 6, whereas the right part of the FIG. 5 depicts a front view 17 of said magnetoelastic body 6.

(35) The magnetoelastic body 6 is any appropriate embodiment which is able to receive stress. The magnetoelastic body 6 comprises at least one magnetoelastic active zone 3, 7, which allows the body to receive a stress. The magnetoelastic zones 3, 7 may be an integral and homogeneous part of the magnetoelastic body 6. It may be constructed as a shaft, a cylinder or any appropriate geometric configuration. It may be rotatable. Thus, it is subject to a magnetoelastic effect.

(36) According to the invention there is at least one sensor 18 comprising at least one channel 1, measuring the stress applied to a magnetoelastic body 6 and at least one channel 2 detecting the external magnetic field.

(37) Said sensor 18 comprises at least one first channel 1 and a second channel 2.

(38) In the example shown in the FIG. 5 the channel 1 is measuring the stress and detects to some extend the external magnetic field. The other channel 2 detects the external magnetic field only.

(39) Said channel 1 is set up as a common mode rejection. The channel 2, however is formed in common mode acceptance.

(40) Turning now in detail to the coils and channels according to FIGS. 5a and 5b.

(41) Each magnetic zone 3, 7 of the magnetoelastic body 6 is assigned at least one coil 8, 9 of a sensor 18 measuring the effect of stress applied to the magnetoelastic body 6 and detecting the effect of the external magnetic field to the magnetoelastic body 6.

(42) Since there are at least two magnetic zones 3, 7, also at least two coils 8, 9 are provided each of them being assigned to its corresponding magnetic zone 3, 7.

(43) In the area of the magnetic zones 3, 7 corresponding coils 8, 9 of said channel 1 and said channel 2 are arranged tangentially spaced from said magnetoelastic body 6. The total number of coils in this example is four. In a front view the coils 8, 9 of the channels 1 and 2 are positioned adjacent to each other. They are also positioned axially relative to the magnetoelastic body 6.

(44) The results of this setting in relation to each other are specific signals.

(45) The signals generated by the coils 8, 9 respectively, are further processed by the above mentioned channels 1 and 2.

(46) According to the two sets of magnetic zone-related information, the first channel 1 evaluates a first signal. Likewise the second channel 2 evaluates a second signal.

(47) The coils 8, 9 of the one channel 1 are connected in common mode rejection; the coils of the other channel 2 are connected in common mode acceptance.

(48) This means that the method employs a Dual-band system, of which the magnetic zones 3, 7 are read with at least one channel 1, configured in common mode rejection. The other channel 2 is set in common mode acceptance.

(49) Turning to the side view 16 of the magnetoelastic body 6. The side view 16 of the FIG. 5 shows coils 8, 8′ and 9, 9′. Said coils 8′ and 9′ refer to the channel 2, whereas the coils 8 and 9 refer to the channel 1. Thus, the coils 8 and 9 are positioned for measuring the stress applied to the magnetoelastic body 6.

(50) In the side view of FIG. 5a, the channel 1 and its coils 8, 9 are set in the common mode rejection, whereas the channel 2 and the corresponding coils 8′, 9′ are set in the common mode acceptance.

(51) Turning now to the FIGS. 6 and 7, both focusing on the coils 8, 9 of the channels 1 and 2 and on the current 11 as well as on the varying directions 14, 15 of the flows 12, 13 of the current 11 within said coils 8 and 9.

(52) In the common mode rejection configuration of the channel 1, shown in said FIG. 6 said coils 8, 9 are arranged in a common mode rejection.

(53) The presentation of the channel 2 shown in the FIG. 7 represents common mode acceptance connection state of said coils 8, 9.

(54) Turning now to the FIG. 6. The FIG. 6 is a diagram of the coils 8, 9 of the channel 1, operating in the common mode rejection configuration.

(55) Reference 19 and reference 20 indicate the external magnetic field detected by the channel 1 and the channel 2.

(56) References 21 and 22 stand for the stress-induced magnetic fields.

(57) The stress induced magnetic fields 21, 22 are of the same magnitude and opposite direction. This is due to the design and the processing of the magnetic zone 3, 7.

(58) The arrows 23 and 24 show the sensitive direction of the channel 1. Thus, the arrows 23, 24 show directions of the measurement of the magnetic field 19 of channel 1.

(59) In the common mode rejection configuration of channel 1, the arrows 23 and 24 are arranged opposite to each other. In a common mode rejection configuration the following formula is relevant: The result of the measurement of the channel 1 represents the stress induced magnetic field 21, whereas in a common mode acceptance configuration the channel 2 outputs a signal which represents the external magnetic field 20.

(60) The external magnetic field may be comprised of a far field noise source, a near field noise source or even both.

(61) Turning now to FIG. 7 which shows a diagram of the Channel 2 which operates in common mode acceptance.

(62) Said channel 2 detect an external magnetic field, shown by references 19, 20.

(63) The stress induced magnetic field sensed by the channel 2 respectively is indicated by reference numbers 21, 22.

(64) According to the design and the processing of the magnetic zones 3, 7 the stress induced magnetic field 21, 22 of the channel 2 is of equal magnitude and is directed in a opposite manner, relative to each other.

(65) The arrows 23, 24 shown in the FIG. 7 indicate the sensitive direction or the positive direction of the result of the measurement of the channel 2 respectively.

(66) When the channel 2 is operated in common mode acceptance (see FIG. 7), the corresponding coils 8, 9 are oriented in a way that the arrows 24 are leading in the same direction.

(67) In the common mode rejection configuration the channel 1 outputs a signal representing a stress induced magnetic field. The channel 2 outputs a signal, representing the external magnetic field 20.

(68) The measured output of the sensor comprising the channel 1 in common mode rejection=the stress induced magnetic field 21, 22 of one of the magnetic zones 3, 7−the stress induced magnetic field 21, 22 from the other magnetic zone 3, 2+the zone of the external magnetic field 19, 20 detected at both the channel 1 and 2.

(69) While various embodiments have been described above, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of a preferred embodiment should not be limited by any of the above-described exemplary embodiments.

REFERENCE LIST

(70) 1 Channel 1 2 Channel 2 3 Magnetic zone 4 Direction of magnetization 5 Direction of magnetization 6 Magnetic elastic body 7 Magnetic zone 8 Coil 8′ Coil 9 Coil 9′ Coil CT Tap 11 Current 12 Flow of current 13 Flow of current 14 Direction of flow 15 Direction of flow 16 Side view 17 Front view 18 Sensor 19 External magnetic field 20 External magnetic field 21 Stress induced magnetic field 22 Stress induced magnetic field 23 Arrow —Sensitive direction —Positive direction —Field measurement 24 Arrow —Sensitive direction —Positive direction —Field measurement