CN114061799B - Wheatstone bridge and multidimensional force sensor - Google Patents
Wheatstone bridge and multidimensional force sensor Download PDFInfo
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- CN114061799B CN114061799B CN202111314517.4A CN202111314517A CN114061799B CN 114061799 B CN114061799 B CN 114061799B CN 202111314517 A CN202111314517 A CN 202111314517A CN 114061799 B CN114061799 B CN 114061799B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/20—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
- G01L1/22—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges
- G01L1/225—Measuring circuits therefor
- G01L1/2262—Measuring circuits therefor involving simple electrical bridges
Abstract
The application relates to a Wheatstone bridge and a multidimensional force sensor. The Wheatstone bridge comprises four bridge arms, each bridge arm comprises a plurality of resistors, the number of the resistors in each bridge arm is the same, the reference resistance values of the resistors are the same, the resistors in each bridge arm are in a preset series-parallel structure, the equivalent resistors of the resistors are equal to the resistance value of a single resistor in the preset series-parallel structure, and the resistors are used for balancing the temperature difference of the single resistor. The bridge arm of a single resistor is replaced by the mode that a plurality of resistors form a bridge arm according to a preset series-parallel structure, on the basis of not changing the original output characteristic of a circuit, individual temperature differences are offset and balanced by a plurality of resistors with the same or similar temperature characteristics, so that the influence of the resistance value difference of the bridge arm resistors on differential output signals of the Wheatstone bridge caused by temperature change is reduced, and the technical problem that the influence of the resistance value temperature difference of strain gauges of the Wheatstone bridge on the differential output signals is overlarge is solved.
Description
Technical Field
The application relates to the technical field of multidimensional force sensors, in particular to a Wheatstone bridge and a multidimensional force sensor.
Background
The multidimensional force sensor can sense the force and the moment in each direction in space due to the special and exquisite structural combination and the decoupling of a software algorithm, wherein the detection scheme of the Wheatstone bridge formed by the strain gauges becomes more choices of the design of the multidimensional force sensor due to the comprehensive advantages of precision, cost and the like, and is widely applied to assembly robots, sorting robots and cooperative robots. However, in high-temperature working environments such as welding and polishing, the robot using the multi-dimensional force sensor is subjected to high temperature, so that the accuracy and performance of the multi-dimensional force sensor are greatly affected, and output signals of a detection part are unstable, even the robot fails. The weak asynchronism of the resistance value caused by the temperature difference of the resistance values of the strain gauges of the Wheatstone bridge can cause the great change of the differential output signal, which is the root cause of the rapid reduction of the precision of the multidimensional force sensor at high temperature.
At present, in the related art, strain gauges of the same type and produced in the same batch need to be selected as much as possible, or a temperature compensation sensor is adopted as a bridge arm (i.e., a strain gauge) of a wheatstone bridge, so that when the temperature of other bridge arms of the wheatstone bridge changes, the resistance variation of the temperature compensation sensor is equal to the resistance variation of the other bridge arms. However, in the production process of the strain gauge, even if the strain gauges are of the same type and the same batch, the temperature characteristics of the strain gauges cannot be guaranteed to be completely consistent, because in the production process, manufacturers or production technologies only guarantee the requirement of strain gauge strain characteristic consistency and cannot completely guarantee the strain gauge temperature characteristic consistency, so that the precision of the six-dimensional force sensor fails due to the temperature difference characteristic of each strain gauge under the requirement of high precision and high performance even if small difference exists. The mode that the temperature compensation sensor is used as a Wheatstone bridge arm can lead the temperature characteristics of the temperature compensation sensor and another strain gauge connected with an output end to tend to be consistent, but the strain characteristics can not be kept consistent, moreover, one temperature compensation sensor can not be kept consistent with the temperature characteristics of three strain gauges, therefore, a plurality of temperature compensation sensors are needed to be arranged, more problems are brought to the situation, if the consistency of the strain characteristics of four strain gauges can not be kept, the precision and the performance of the force sensor are more landslide, and the original purpose of ensuring the consistency of the temperature characteristics of the strain gauges to improve the precision and the performance of the force sensor is violated.
Aiming at the problem that the influence of the resistance temperature difference of the strain gauges of the Wheatstone bridge on the differential output signals is too large, an effective solution is not provided at present.
Disclosure of Invention
The application provides a Wheatstone bridge and multidimensional force sensor to solve the technical problem that the influence of the resistance temperature difference of strain gauges of the Wheatstone bridge on differential output signals is too large.
According to an aspect of an embodiment of the present application, the present application provides a wheatstone bridge, including four bridge arms, each bridge arm includes a plurality of resistors, the number of the plurality of resistors in each bridge arm is the same, the reference resistance values of the plurality of resistors are the same, the plurality of resistors in each bridge arm adopt a preset series-parallel structure, in the preset series-parallel structure, the equivalent resistors of the plurality of resistors are equal to the resistance values of a single resistor, and the plurality of resistors are used for balancing the temperature difference of the single resistor.
Alternatively, the plurality of resistances are resistances whose temperature difference coefficients follow a normal distribution of 1.
OptionallyThe number of the plurality of resistors of each bridge arm is n 2 Wherein n is a natural number greater than or equal to 2.
Optionally, the preset series-parallel structure adopted by the plurality of resistors includes: n groups of parallel units, wherein each group of units is connected in series by n resistors.
Optionally, in n 2 In the case of an exponent of 4, the preset series-parallel structure adopted by the plurality of resistors further includes: the embedded multi-stage unit is characterized in that a father unit is formed by connecting 4 child units in parallel after being connected in pairs; under the condition that the next level of the child unit exists in the child unit, the structure of the child unit is the same as that of the parent unit, wherein the leaf unit is formed by connecting 4 resistors in series in pairs and then in parallel, and the leaf unit is the minimum unit of the multi-level unit.
Optionally, the dependence of the equivalent resistance of each bridge arm on temperature is as follows:
wherein j is 1, 2, 3, 4, Rj' T The resistance value of the equivalent resistance of each bridge arm at the temperature T,
is the resistance value of the ith resistor in m rows in the plurality of resistors in each bridge arm, a t Is the temperature coefficient of each resistor, K m*i Is the temperature coefficient of variation of the ith resistor in the m rows.
Optionally, the differential output signal of the wheatstone bridge is:
and Rt' is a difference value of resistance value of the resistor based on the reference temperature along with the change of the temperature, and E is a power supply voltage of the Wheatstone bridge.
According to another aspect of embodiments of the present application, there is provided a multi-dimensional force sensor comprising the wheatstone bridge described above.
Alternatively, the resistance of the arms constituting the wheatstone bridge is a strain gauge resistance having uniform strain characteristics.
Optionally, all the strain gauges on the same bridge arm are attached to the same deformation position of the deformation structure to be detected.
Compared with the related art, the technical scheme provided by the embodiment of the application has the following advantages:
the application provides a Wheatstone bridge, including four bridge arms, every bridge arm all includes a plurality of resistances, and the quantity of a plurality of resistances is the same in every bridge arm, and a plurality of resistances adopt predetermineeing the series-parallel structure in every bridge arm, predetermine the series-parallel structure and set up to make the equivalent resistance of a plurality of resistances equal with the resistance of single resistance. The structure that a resistance in the basic Wheatstone bridge is taken as the bridge arm is changed into the mode that a bridge arm is formed by a plurality of resistances according to the preset series-parallel structure, on the basis of not changing the original output characteristic of the circuit, individual temperature difference is removed through hedging and balancing by a plurality of resistances with the same or similar temperature characteristics, thereby reducing the influence of the resistance difference of the bridge arm resistances brought by temperature change on differential output signals of the Wheatstone bridge, and solving the technical problem that the influence of the resistance temperature difference of strain gauges of the Wheatstone bridge on the differential output signals is overlarge.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and together with the description, serve to explain the principles of the application.
In order to more clearly illustrate the technical solutions in the embodiments or related technologies of the present application, the drawings needed to be used in the description of the embodiments or related technologies will be briefly described below, and it is obvious for those skilled in the art to obtain other drawings without any creative effort.
FIG. 1 is a schematic diagram of an alternative Wheatstone bridge provided by an embodiment of the present application;
fig. 2 is a schematic diagram of an alternative preset series-parallel structure provided in an embodiment of the present application;
FIG. 3 is a schematic diagram of an alternative basic Wheatstone bridge provided in accordance with an embodiment of the present application;
FIG. 4 is a comparison of temperature difference characteristics provided by embodiments of the present application;
FIG. 5 is a schematic diagram of a multi-dimensional force sensor provided in an embodiment of the present application;
FIG. 6 is a schematic diagram of an alternative Wheatstone bridge according to an embodiment of the present application.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
In the following description, suffixes such as "module", "component", or "unit" used to denote elements are used only for the convenience of description of the present application, and have no specific meaning in themselves. Thus, "module" and "component" may be used in a mixture.
In the related art, in order to reduce the influence of temperature change on the differential output signal of the wheatstone bridge, strain gauges of the same type and produced in the same batch need to be selected as much as possible, or a temperature compensation sensor is adopted as a bridge arm (i.e., a strain gauge) of the wheatstone bridge, so that when the temperature of other bridge arms of the wheatstone bridge changes, the resistance variation of the temperature compensation sensor is equal to the resistance variation of the other bridge arms. However, in the production process of the strain gauge, even if the strain gauges are of the same type and the same batch, the temperature characteristics of the strain gauges cannot be guaranteed to be completely consistent, because in the production process, manufacturers or production technologies only guarantee the requirement of strain gauge strain characteristic consistency and cannot completely guarantee the strain gauge temperature characteristic consistency, so that the precision of the six-dimensional force sensor fails due to the temperature difference characteristic of each strain gauge under the requirement of high precision and high performance even if small difference exists. The mode that the temperature compensation sensor is used as a Wheatstone bridge arm can lead the temperature characteristics of the temperature compensation sensor and another strain gauge connected with an output end to tend to be consistent, but the strain characteristics can not be kept consistent, moreover, one temperature compensation sensor can not be kept consistent with the temperature characteristics of three strain gauges, therefore, a plurality of temperature compensation sensors are needed to be arranged, more problems are brought to the situation, if the consistency of the strain characteristics of four strain gauges can not be kept, the precision and the performance of the force sensor are more landslide, and the original purpose of ensuring the consistency of the temperature characteristics of the strain gauges to improve the precision and the performance of the force sensor is violated.
In order to solve the problems mentioned in the background art, according to an aspect of the embodiments of the present application, an embodiment of a wheatstone bridge is provided, as shown in fig. 1, the wheatstone bridge includes four bridge arms, each bridge arm includes a plurality of resistors, the number of the plurality of resistors in each bridge arm is the same, reference resistance values of the plurality of resistors are the same, the plurality of resistors in each bridge arm adopt a preset series-parallel structure, in the preset series-parallel structure, the equivalent resistors of the plurality of resistors are equal to the resistance value of a single resistor, and the plurality of resistors are used for equalizing temperature differences of the single resistor.
In the embodiment of the application, E + is a power supply input end of a Wheatstone bridge, a first bridge arm is formed between E + and S +, a second bridge arm is formed between E + and S-, a third bridge arm is formed between S-and GND, a fourth bridge arm is formed between S + and GND, S + is a connection output end of the first bridge arm and the fourth bridge arm, and S-is a connection output end of the second bridge arm and the third bridge arm. Taking the first bridge arm as an example, each bridge arm comprises a plurality of resistors, the number of the plurality of resistors in each bridge arm is the same, the resistance values and the types of the plurality of resistors are also the same, and when the reference resistance value is 30 ℃, the resistance value of each resistor is 120 Ω. The plurality of resistors in each bridge arm are in a preset series-parallel structure, and the preset series-parallel structure is set to enable the equivalent resistors of the plurality of resistors to be equal to the resistance value of a single resistor.
Due to the fact that the preset series-parallel connection structure is adopted, the equivalent resistances of the resistors are equal to the resistance of the single resistor, the Wheatstone bridge with the bridge arms formed by the same resistors is consistent with the circuit output characteristics of the basic Wheatstone bridge with one resistor as the bridge arm, the individual differences of the resistors are balanced, the equivalent resistances of the bridge arms are enabled to change consistently along with the change of temperature, the situation that the equivalent resistance of the single bridge arm is greatly different from the equivalent resistances of other bridge arms is avoided, and the influence of the temperature on differential output signals of the Wheatstone bridge is further reduced. The temperature characteristics of the plurality of resistors, the number of resistors, the predetermined series-parallel structure, and the like will be described below.
Alternatively, the plurality of resistances are resistances whose temperature difference coefficients follow a normal distribution of 1.
In the embodiment of the application, in order to reduce the influence of the individual temperature characteristic difference on the whole as much as possible, a plurality of resistors with the temperature difference coefficients following the normal distribution of 1 can be selected, and the temperature characteristics of most resistors are ensured to be consistent, so that the influence of the individual difference is balanced.
Optionally, the number of the plurality of resistors of each bridge arm is n 2 Wherein n is a natural number greater than or equal to 2.
In the embodiment of the application, in order to meet the requirement that the plurality of resistors are arranged according to the preset series-parallel structure so that the equivalent resistance of each bridge arm is equal to the resistance of a single resistor, the number of the plurality of resistors to be arranged is n 2 Wherein n is a natural number greater than or equal to 2.
Optionally, the preset series-parallel structure adopted by the plurality of resistors includes: n groups of parallel units, wherein each group of units is connected in series by n resistors.
In the embodiment of the present application, taking the first bridge arm shown in fig. 1 as an example, n in each bridge arm 2 The resistors can be arranged in a matrix of n rows and n columns to form n groups of parallel units, each group of units comprising n resistors connected in series, namely R1 1*1 And R1 2*1 ～R1 n*1 In series, R1 1*2 And R1 2*2 ～R1 n*2 In series, R1 1*3 And R1 2*3 ～R1 n*3 In series, R1 1*n And R1 2*n ～R1 n*n The groups are connected in series and then connected in parallel. The equivalent resistance of the plurality of resistors in the series-parallel structure is equal to the resistance of one resistor through calculation of the equivalent resistance.
Optionally, in n 2 In the case of an exponent of 4, the preset series-parallel structure adopted by the plurality of resistors further includes: the embedded multi-stage unit is characterized in that a father unit is formed by connecting 4 child units in parallel after being connected in pairs; under the condition that the next level of the child unit exists in the child unit, the structure of the child unit is the same as that of the parent unit, wherein the leaf unit is formed by connecting 4 resistors in series in pairs and then in parallel, and the leaf unit is the minimum unit of the multi-level unit.
In the embodiment of the application, the equivalent resistance and the resistance of a single resistor can be equal through other series-parallel structures under the condition that the number of the resistors of each bridge arm is 4, 16, 64 and other 4 indexes, and n is used for 2 For example, as shown in fig. 2, in the preset series-parallel structure, 16 resistors between the upper port and the lower port form a bridge arm, the overall equivalent resistance of the bridge arm is R1, the equivalent resistance R1 is formed by connecting two 4 units in series and then connecting them in parallel, and if the equivalent resistance of each unit is R1 1*1 ′、R1 1*2 ′、R1 2*1 ′、R1 2*2 ', one of the equivalent resistances is R1 1*1 ' in turn, 4 smaller cells (i.e., resistor R1) 1*1 、R1 1*2 、R1 2*1 、R1 2*2 ) Two of the two are connected in series and then are connected in parallel. Therefore, in the series-parallel structure, the equivalent resistor R1 is a parent unit, and the equivalent resistor R1 is 1*1 ′、R1 1*2 ′、R1 2*1 ′、R1 2*2 ' is 4 child cells constituting a parent cell R1, and the equivalent resistance is R1 1*1 ' As parent cell, resistor R1 1*1 、R1 1*2 、R1 2*1 、R1 2*2 And as a constituent parent unit R1 1*1 A subunit of. And when 4 sub-cells constituting one cell are resistors, the cell is a leaf cell, i.e., the minimum cell constituting a multi-level cell.
Optionally, the dependence of the equivalent resistance of each bridge arm on temperature is as follows:
wherein j is 1, 2, 3, 4, Rj' T The resistance value of the equivalent resistance of each bridge arm at the temperature T,
is the resistance value of the ith resistor in m rows in the plurality of resistors in each bridge arm, a t Is the temperature coefficient of each resistor, K m*i Is the temperature coefficient of difference of the ith resistance of the m rows.
Optionally, the differential output signal of the wheatstone bridge is:
and Rt' is a difference value of resistance value of the resistor based on the reference temperature along with the change of the temperature, and E is a power supply voltage of the Wheatstone bridge.
A basic wheatstone bridge (using one resistor as the bridge arm) is shown in fig. 3. The differential output signal of the basic wheatstone bridge is:
and E is a Wheatstone bridge supply voltage.
In the basic wheatstone bridge, the resistance depends on temperature as follows:
wherein the content of the first and second substances,
is the resistance value of each bridge arm at temperature T, a t Is the temperature coefficient, k, of each resistance n Is a temperature difference coefficient of each resistor, n is 1, 2,3,4. The differential output signal of the basic wheatstone bridge is then:
the simplification is as follows:
as can be seen from the above formula, due to the existence of the characteristic of the resistance temperature difference of each bridge arm, when the resistance value of any one bridge arm in the bridge circuit, or the resistance values of the upper and lower arm combination and the left and right arm combination resistors changes with the temperature, the resistance values of the bridge arms are inconsistent with each other, so that the difference exists, and the differential output signal Vo is output t The difference characteristic is a value which changes with the temperature difference characteristic K of each resistor, and the difference characteristic changes more intensely with the change with the temperature.
For convenience of explanation, the above formula is simplified:
such as: when the environment temperature is 30 ℃, the measured values of the resistances of the four bridge arm strain gauges are respectively as follows: r1 is 121.30 omega, R2 is 121.36 omega, R3 is 121.37 omega, and R4 is 121.50 omega. And Rt is a difference value of resistance and temperature of the reference strain gauge based on the environment temperature of 30 ℃, if Rt is 0 at 30 ℃, and if E is 3.3V, the differential output signal at 30 ℃ is 1291uV according to the formula. When the ambient temperature is 80 deg.c, the difference Rt of the resistance values is 0.12 Ω due to the influence of the temperature, and the differential output signal becomes 474 uV. The output signal curve is shown in fig. 4. The circular mark is the situation when the resistance value difference exists, the rectangular mark is the situation when the resistance value difference does not exist (namely, in an ideal situation, all resistance temperature characteristics of the bridge arm are consistent), the abscissa is the temperature, and the higher the temperature is, the larger the resistance value difference Rt is. The ordinate is the output signal of the bridge, the unit is uV, and therefore it can be seen that the differential output signal generates great change due to the weak asynchronism of the resistance value caused by the temperature difference of the resistance values of the bridge arms.
Theoretically, when the ambient temperature changes, the resistance values of the bridge arms should be ensured to be the same, so that the output signals of the Wheatstone bridge are ensured not to be influenced by the temperature, but the difference is inevitable in the actual situation, and the application balances the individual difference by adopting a multi-resistance mode, and reduces the influence of the temperature on the differential output signals of the Wheatstone bridge.
In the application, each bridge arm can use n 2 The equivalent resistance of each bridge arm is dependent on the temperature by the following relation:
the differential output signal of the wheatstone bridge is:
if n is used for each bridge arm 2 The resistance of the whole resistor after series and parallel connection is as large as that of a single resistor, but the temperature difference is averaged, and the error caused by the temperature is reduced to 1/n of the original error 2 Namely:
wherein, Δ Vo t Variation value of basic Wheatstone bridge differential output signal due to temperature influence signal, delta Vo' t The change value of a Wheatstone bridge differential output signal adopting a plurality of resistors due to temperature influence is realized.
Therefore, by adopting the technical scheme, the influence of the resistance value difference of the bridge arm resistors caused by temperature change on the differential output signals of the Wheatstone bridge can be effectively reduced.
According to another aspect of embodiments of the present application, there is provided a multi-dimensional force sensor comprising the wheatstone bridge described above.
The multi-dimensional force sensor principle is as shown in fig. 5, deformation can be generated when a structural beam of the force sensor is stressed or moment, and the multi-dimensional force sensor enables force or moment loaded in a specific direction to be changed only by a strain gauge adhered to a specific position on the beam through a unique structure, so that under the condition that given power supply voltage is certain, a controller collects differential output signal voltage of a Wheatstone bridge, and after the differential output signal voltage is processed through a specific algorithm, values of the loading force and the moment in the specific direction can be displayed on an upper computer.
If the temperature characteristics of the strain gauges of the bridges are inconsistent under the high-temperature working environment of the multi-dimensional force sensor, output signals of the bridges in a software algorithm of the multi-dimensional force sensor affect and couple with each other in the algorithm, even if the temperature characteristics of the strain gauges in one bridge are inconsistent, the display precision of each direction of the multi-dimensional force sensor is affected, and the high-temperature abnormality of the multi-dimensional force sensor is directly caused. Such as: when looking up a data manual published by a six-dimensional force sensor of a certain company with strong force in foreign industries, the six-dimensional force sensor indicates that the precision of the sensor is only 7% under the condition of 72 ℃ working temperature, and the precision is 0.1% under the condition of room temperature. Therefore, the influence of high temperature on the sensor is not eliminated by the company products with strong force in the industry. For another example: the six-dimensional force sensor of a certain domestic company has the condition when actually measuring the temperature, the precision can reach 0.5 percent under the condition of room temperature, and the precision is only 8 percent at the temperature of 80 ℃.
In the multidimensional force sensor provided by the application, due to the adoption of the Wheatstone bridge structure, the temperature difference of the strain gauge is reduced to 1/n of the temperature difference of the conventional multidimensional force sensor 2 And moreover, the error caused by the temperature difference characteristic at high temperature is small enough to meet the high-precision application, so that the performance of the multidimensional force sensor at high temperature can be greatly improved, and the actual measurement result also shows that the change of the Wheatstone bridge structure does not influence other performances of the multidimensional force sensor.
Alternatively, the resistance of the arms constituting the wheatstone bridge is a strain gauge resistance having uniform strain characteristics.
In the related art, even if the strain gauge is of the same type, the temperature characteristics of the strain gauge cannot be guaranteed to be completely consistent in the production process of the strain gauge. In the production process, manufacturers or production technologies only need to ensure the strain characteristic consistency of the strain gauges, and can not completely ensure the temperature characteristic consistency of the strain gauges, so that the precision of the six-dimensional force sensor can be failed due to the temperature difference characteristic of each strain gauge under the requirement of high precision and high performance even if small difference exists.
By adopting the technical scheme, the temperature difference characteristic of a single strain gauge can be ignored without sacrificing the strain characteristic consistency of the strain gauges, and the number of the strain gauges of each bridge arm of the Wheatstone bridge is n 2 Only by ensuring that the temperature difference coefficients of all the strain gauges follow a normal distribution of 1, such as K being 1.01, 1.02, 0.99, 0.98, etc., a small number of differences can be balanced by a large number.
In practical design, due to the requirement of high performance and high precision of the six-dimensional force sensor, the difference output signals of the Wheatstone bridge circuit at high temperature cannot have 20uV voltage change, otherwise, the performance of keeping high precision at the designed high temperature can be directly influenced, and the application can be realized by only changing the structure of the Wheatstone bridge circuit. In the following, a wheatstone bridge of force sensors is described using 4 strain gauges for each arm.
As shown in FIG. 6, the temperature deviation is equalized by using four strain gauges of the same type for each bridge arm, and the strain gauge for the first bridge arm
Temperature compensation is carried out, and the equivalent resistance after compensation is R1' T For the second bridge arm
Temperature compensation is carried out, and the equivalent resistance after compensation is R2' T For the third arm
Temperature compensation is carried out, and the equivalent resistance after compensation is R3' T Of 1 atFor four arms
Temperature compensation is carried out, and the equivalent resistance after compensation is R4' T . The compensated bridge arm resistance and temperature dependence relationship is as follows:
wherein j is 1, 2, 3, 4, which respectively represents the compensated first, second, third, and fourth arms. The differential output signal is as follows:
the concentration of the compensated resistance value is increased by 4 times, and the temperature difference is reduced to 1/4, namely:
optionally, all the strain gauges on the same bridge arm are attached to the same deformation position of the deformation structure to be detected.
In the embodiment of the application, in order not to affect other performances such as resolution of the multi-dimensional force sensor, the strain gauges on the same bridge arm need to be adhered to the same deformation position corresponding to the deformation structure (structural beam) to be detected, and the resolution performance of the multi-dimensional force sensor is affected without adhesion and non-corresponding adhesion.
In addition, as long as the wheatstone bridge differential output signal is adopted to obtain the corresponding physical quantity, the wheatstone bridge differential output signal can be adaptively adjusted based on the scheme of the wheatstone bridge to reduce the error caused by the temperature, and the wheatstone bridge differential output signal is not necessarily a strain gauge sensitive element for measuring the force, and may be a capacitance sensitive element for measuring the force change, an inductance sensitive element for measuring the force, and the like. The Wheatstone bridge circuit is adopted, and the bridge arm is used for detecting the sensitive element of physical change, so that the influence caused by temperature can be attenuated by adopting the scheme, the temperature stability of the detection part of the sensor is improved, and the temperature performance of the whole sensor is improved.
The previous description is only an example of the present application, and is provided to enable any person skilled in the art to understand or implement the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (7)
1. A Wheatstone bridge comprises four bridge arms and is characterized in that each bridge arm comprises a plurality of resistors, the number of the resistors in each bridge arm is the same, the reference resistance values of the resistors are the same, the resistors in each bridge arm are in a preset series-parallel structure, in the preset series-parallel structure, the equivalent resistors of the resistors are equal to the resistance value of a single resistor, the resistors are used for balancing the temperature difference of the single resistor, the resistors are resistors with the temperature difference obeying the normal distribution of 1, and the number of the resistors in each bridge arm is n 2 The number of the resistors is greater than or equal to 2, and the preset series-parallel structure adopted by the resistors comprises: n groups of parallel units, wherein each group of units is connected in series by n resistors.
2. The Wheatstone bridge according to claim 1, wherein at n, n is 2 Under the condition that the number is 4 times, the preset series-parallel connection structure adopted by the resistors is replaced by: the embedded multi-stage unit is characterized in that a father unit is formed by connecting 4 child units in parallel after being connected in pairs; under the condition that the next level of the child unit exists, the structure of the child unit is the same as that of the father unit, wherein the leaf unit is formed by connecting 4 resistors in parallel after being connected in pairs in series, and the leaf unitThe element is the smallest unit of the multilevel unit.
3. The wheatstone bridge of claim 1, wherein the equivalent resistance of each leg is temperature dependent as:
wherein j is 1, 2, 3, 4, Rj' T The resistance value of the equivalent resistance of each bridge arm at the temperature T,
is the resistance value of the ith resistor in the mth row in the plurality of resistors in each bridge arm, a t Is the temperature coefficient of each resistor, K m*i Is the temperature coefficient of difference of the ith resistance of the m rows.
4. The Wheatstone bridge according to claim 3, wherein the differential output signal of said Wheatstone bridge is:
and Rt' is a difference value of resistance value of the resistor based on the reference temperature along with temperature change, and E is a power supply voltage of the Wheatstone bridge.
5. A multi-dimensional force sensor comprising a wheatstone bridge according to any of the claims 1 to 4.
6. The multi-dimensional force sensor according to claim 5, wherein the resistances of the arms constituting the Wheatstone bridge are strain gauge resistances having uniform strain characteristics.
7. The multi-dimensional force sensor according to claim 5, wherein all strain gauges on the same bridge arm are attached to the same deformation position of the deformation structure to be measured.
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| CN114777970B (en) * | 2022-05-23 | 2023-04-11 | 电子科技大学 | Film strain gauge bridge circuit based on flexible circuit board on high-rigidity force measuring knife handle |
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| GB1472294A (en) * | 1974-12-18 | 1977-05-04 | Welwyn Electric Ltd | Strain measuring device |
| CN1028448C (en) * | 1991-06-21 | 1995-05-17 | 南京航空航天大学 | Decoupling method for strain-type multidimensional force sensor |
| CN104375109B (en) * | 2014-07-25 | 2017-12-29 | 中国计量科学研究院 | A kind of self calibration method of testing of resistance load coefficient |
| CN107101755B (en) * | 2017-06-15 | 2019-04-09 | 西安交通大学 | A kind of strain-type three-dimensional force sensor |
| CN111060237A (en) * | 2019-10-23 | 2020-04-24 | 宁波柯力传感科技股份有限公司 | Bridge circuit of force cell |
| CN111272328B (en) * | 2020-02-25 | 2020-11-06 | 东南大学 | High-sensitivity low-dimensional coupling six-dimensional force sensor |
| CN112414594B (en) * | 2020-11-09 | 2022-04-01 | 中国电子科技集团公司第四十九研究所 | Temperature error correction method for silicon piezoresistive pressure sensor |
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