A processing circuit and method for processing torque signal of harmonic reducer

Abstract

The present invention discloses a processing circuit and a processing method for a torque signal of a harmonic reducer. The signal processing circuit includes a Wheatstone half-bridge circuit module, a signal amplification module, a signal superposition module, a filtering module, an ADC signal acquisition module, an EtherCAT slave communication circuit module and a power supply module. The Wheatstone half-bridge circuit module is composed of two mutually perpendicular resistive strain gauges and two resistors with the same resistance value. The signal of the Wheatstone half-bridge circuit is amplified by the signal amplification module and then enters the signal superposition module. In the signal superposition module, the periodic ripple signal generated by the flexible wheel is eliminated and only the load torque signal remains. After filtering, the load torque signal is converted into a digital signal by the ADC acquisition module to obtain the required digital signal. The required digital signal is uploaded and issued by the EtherCAT slave communication module. The present invention has the characteristics of direct measurement, compact structure, small space occupation, and no additional flexibility for the harmonic reducer and the robot joint.

Description

Technical Field

[0001] The present invention relates to the field of sensing technology and collaborative robot joint transmission, and in particular to a processing circuit and method for a harmonic reducer torque signal. Background Art

[0002] As a deceleration device with large reduction ratio, high precision, small backlash and compact structure, harmonic reducer has been widely used in high-precision transmission, especially in new collaborative robot joints and traditional industrial robot end joints. In order to achieve safe interaction with the external environment and people, increase control accuracy and ease of operation, collaborative robots usually need to have force control function.

[0003] There are usually three existing practices. One is to estimate the torque by indirectly sampling the current feedback of the motor. This method is low-cost but has large errors and is usually used in situations where the accuracy requirements are not too high. Another method is to add a multi-dimensional force sensor to the end of the robot. The load torque can be converted to each joint through a series of complex mathematical solutions for joint force control. This method is expensive and complex to solve. If the external force is not applied to the end joint, the joint solution cannot be performed, so collision detection cannot be implemented and safety is greatly reduced. The last method is to install a torque sensor on each joint to directly read the joint torque for force control. This method can directly avoid the difficulties of complex dynamic solution and parameter identification, and also avoid the problems of noise interference and time delay introduced in the dynamic equation. However, installing an independent torque sensor on each joint will also invisibly add an unnecessary flexible unit, which increases the volume, significantly reduces the overall rigidity and transmission accuracy of the joint, and increases the cost accordingly.

[0004] Since the harmonic reducer decelerates and transmits power through the periodic flexible deformation of the flexwheel, one way to reduce the flexible link is to use the elastic deformation of the harmonic reducer flexwheel to sense the size of the load torque so that the harmonic reducer has a torque sensing function. The current common method is to evenly distribute multiple sets of strain gauges on the end of the harmonic flexwheel in the circumferential direction to realize the sensing of the torque signal. The strain signal sensed by the strain gauge contains the strain signal generated by the load torque and the large deformation signal generated by the periodic motion of the flexwheel. Among them, the strain signal generated periodically by the flexwheel belongs to the ripple noise and must be eliminated. At present, many methods have been proposed to eliminate the ripple signal. One of them is to use Kalman filtering to filter out the clutter and measure the torque value of the load. This method is relatively complex to solve and has the defect of delay, which is not suitable for occasions with high real-time requirements. Another method is to evenly distribute multiple strain gauges on the surface of the flexwheel along its circumference to form a half-bridge circuit, and there are strict angle and position restrictions between the strain gauges. This method requires a relatively high number of strain gauges and a high degree of positioning accuracy, which invisibly increases the installation cost and introduces interference noise. The accuracy will also be greatly reduced as the installation accuracy decreases.

[0005] In addition, in the processing of torque signals, the influence of various electromagnetic interferences is also a factor that cannot be ignored. Therefore, in the selection of torque sensors for collaborative robots, how to improve stiffness, reduce joint flexibility, make the overall joint structure more compact, and make force control simpler and more precise has great practical significance. Summary of the invention

[0006] In view of the shortcomings of the existing methods and the actual needs of torque sensing for collaborative robots, the present invention provides a cap-type harmonic reducer with a torque sensing function, which has a simple and compact structure, convenient strain mounting, timely response, and simple and accurate measurement.

[0007] To achieve the above object, the present invention first provides a method for processing a torque signal of a harmonic reducer, which comprises the following steps:

[0008] 1) Provide a harmonic reducer with torque sensing function, wherein the flexspline of the harmonic reducer is a cap-shaped flexspline, 2N+1 sets of strain gauges are pasted on the bottom of the brim of the cap-shaped flexspline to measure the output torque by using the deformation of the flexspline, where N is an integer greater than or equal to 1; the signal line of the strain gauge passes through the notch of the end cover of the harmonic reducer housing and is connected to a signal processing circuit board; each set of strain gauges is composed of two mutually perpendicular strain gauge units, and the long side or short side of the strain gauge unit is perpendicular to the radius direction of the flexspline;

[0009] 2) The signals of the two mutually perpendicular strain gauge units are led out from the harmonic flexwheel and then connected to the signal processing circuit board and combined with two resistors of the same resistance value to form a Wheatstone half-bridge circuit to sense the load torque signal and the ripple signal generated by the flexwheel;

[0010] The load torque signal and the flexible wheel ripple signal are amplified by the signal amplification module and then enter the signal superposition module; the signal superposition module includes an adjustment resistor adjusted by a digital potentiometer and an operational amplifier addition circuit; the adjustment resistor is used to adjust the signal amplitude so that the output signal peak value after vector superposition is minimized; the signal superposition module removes the ripple signal by means of a hardware circuit;

[0011] The specific implementation process of removing the ripple signal by means of hardware circuit is as follows: when the harmonic reducer is in the no-load state, one set of strain gauge signals is selected as the reference signal, and then the other two sets of strain gauge signals are used as comparison signals. The signal gain is adjusted by a high-precision digital potentiometer so that the vector sum after the synthetic vector and the reference signal vector are superimposed is close to zero; the gain of the signal can be adjusted by a high-precision digital potentiometer to determine the resistance value of the adjustment resistor that should be connected when the sum of the three vector superposition is zero; then a resistor with a corresponding resistance value is selected from the resistor standard library as the adjustment resistor of the signal superposition module; the operational amplifier addition circuit adopts four reverse negative feedback inputs, and the three strain gauge signals are simultaneously connected to the reverse end of the operational amplifier through the corresponding reference resistor or adjustment resistor, and the fourth is to add a bias voltage so that the voltage is in the required range, thereby realizing the removal of the ripple signal by means of hardware circuit; once the standard resistance is determined, under load conditions, the signal superposition module can also filter out the ripple signal by itself, and the resulting signal is the desired load torque signal;

[0012] 3) After removing the ripple signal under no-load conditions, the remaining signal needs to enter the filter module for filtering due to interference from electrical noise or other noise; then the ADC acquisition module performs analog-to-digital conversion on the acquired filtered signal to obtain a digital signal;

[0013] 4) The EtherCAT slave communication module transmits the digital signal to the next-level EtherCAT slave communication module or the host computer for use as a torque sensing signal.

[0014] As an optional solution of the present invention, the strain gauges are selected into three groups, and the three groups of strain gauges are kept at intervals of 120 degrees in the circumferential position; each group of strain gauges is a strain rosette structure perpendicular to each other.

[0015] The present invention also provides a processing circuit for a harmonic reducer torque signal, which comprises:

[0016] The Wheatstone half-bridge circuit module connects each set of strain gauge signals from the harmonic reducer to the signal processing circuit board and forms a Wheatstone half-bridge circuit with two resistors of the same resistance value to sense the load torque signal and the ripple signal generated by the flexible wheel;

[0017] A signal amplification module, used to amplify the load torque signal and the flexible wheel ripple signal;

[0018] The signal superposition module includes an adjustment resistor and an operational amplifier addition circuit adjusted by a digital potentiometer; the adjustment resistor is used to adjust the signal amplitude so that the peak value of the output signal after vector superposition is minimized; the signal superposition module removes the flexible wheel ripple signal by means of a hardware circuit; the implementation process of the signal superposition module removing the ripple signal by means of a hardware circuit is specifically as follows: when the harmonic reducer is in an unloaded state, one set of strain gauge signals is selected as a reference signal, and then the other two sets of strain gauge signals are used as comparison signals, and the signal gain is adjusted by a high-precision digital potentiometer so that the vector sum after the synthetic vector and the reference signal vector are superimposed is close to zero; the high-precision digital potentiometer is adjusted The gain of the signal is adjusted and the resistance value to be connected when the sum of the three vector superposition is zero is determined; then a resistor with the corresponding resistance value is selected from the resistor standard library as the adjustment resistor; the operational amplifier addition circuit adopts four reverse negative feedback inputs, and the three strain gauge signals are simultaneously connected to the reverse end of the operational amplifier through the corresponding reference resistor or adjustment resistor. The fourth path is to add a bias voltage so that the voltage is in the required range, thereby realizing the removal of the ripple signal through the hardware circuit; once the standard resistance is determined, under load conditions, the signal superposition module can also filter out the ripple signal by itself, and the obtained signal is the required load torque signal, thereby realizing the removal of the ripple signal through the hardware circuit;

[0019] A filtering module, which performs filtering on the signal processed by the signal superposition module;

[0020] The ADC acquisition module performs analog-to-digital conversion on the filtered signal to obtain a digital signal;

[0021] The EtherCAT slave communication module transmits the digital signal obtained by the ADC acquisition module to the next-level EtherCAT slave communication module or the host computer for use as a torque sensor signal; and

[0022] The power supply module provides power to each module, and the power supply module can provide -5 volts, 3.3 volts and 5 volts of power.

[0023] As a preferred solution of the present invention, the signal amplification module includes a signal differential input circuit and a signal amplification circuit; the signal differential input circuit ensures the stability of the input signal; and the signal amplification circuit amplifies the signal to the volt level.

[0024] As a preferred solution of the present invention, the operational amplifier adding circuit of the signal superposition module adopts an inverse proportional adder.

[0025] As a preferred solution of the present invention, the filtering module is composed of a tenth-order low-pass filter and a follower; the tenth-order low-pass filter performs low-pass filtering on the output signal of the previous stage; and the follower is used to increase the output impedance of the circuit.

[0026] As a preferred solution of the present invention, the ADC signal acquisition module uses a 24-bit micro-power industrial frequency suppression ADC to perform analog-to-digital conversion and acquire the signal.

[0027] As a preferred solution of the present invention, the EtherCAT slave communication module is communicatively connected with the ADC acquisition module, and transmits the final signal to the next-level EtherCAT slave communication module or the host computer for processing via Ethernet.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] Directly using the flexibility of the harmonic reducer flexwheel as the carrier of torque detection, there is no need to add additional flexible units, and there is no need to solve complex joint torques, which has the advantage of direct measurement. In addition, the structure is simpler and more compact, with a smaller size, and easier to integrate with other components such as motors. Since there is only one flexible unit, there is no coupling problem in torque measurement, so the measurement accuracy will also be improved. In addition, due to the use of hardware ripple removal, the signal can be processed in real time, thereby avoiding the delay problem caused by software processing of the signal. In addition, the requirements for the pasting position and angle of the strain gauge will be greatly reduced. When pasting, just place the strain gauge at an approximate position and angle. This can greatly reduce the influence of human factors and save the labor cost of pasting strain gauges, making the mounting of strain gauges simpler and signal acquisition simpler and more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The overall structure diagram of the harmonic reducer flexspline with strain gauges and input and output shafts attached thereto of the present invention;

[0031] Figure 2 It is a schematic diagram of the arrangement of the strain gauge group on the flexspline of the present invention;

[0032] Figure 3 It is an axonometric view of the pasting position of the strain gauge group of the present invention;

[0033] Figure 4 This is a diagram of the torque signal processing scheme of the present invention;

[0034] Figure 5 This is the circuit diagram of the signal amplification module;

[0035] Figure 6 This is the circuit diagram of the signal superposition module;

[0036] Figure 7 It is the circuit diagram of the filter module and the follower;

[0037] Figure 8a For power module circuit Figure 1 ;

[0038] Figure 8b For power module circuit Figure 2 .

[0039] 1-integrated wave generator and input shaft, 2-housing end cover, 3-strain gauge, 4-flexible wheel, 5-cross roller bearing inner ring, 6-rigid wheel, 7-output flange, 8-flexible bearing, 9-cross roller bearing outer ring. DETAILED DESCRIPTION

[0040] The present invention is further described and illustrated below in conjunction with specific embodiments. The embodiments are merely exemplary of the present disclosure and do not define the scope of limitation. The technical features of each embodiment of the present invention may be combined accordingly without conflicting with each other.

[0041] like Figure 1-3 As shown, a harmonic reducer with torque sensing function includes a rigid wheel 6, a flexible wheel 4, a wave generator, a cross roller bearing, an input and output assembly and a strain gauge 3; the flexible wheel is a cap-shaped flexible wheel, and the outer gear ring of the cap-shaped flexible wheel is placed in the cavity of the rigid wheel and realizes internal meshing transmission with the inner gear ring of the rigid wheel; the brim of the cap-shaped flexible wheel is fixed with the outer ring 9 of the cross roller bearing and the shell end cover 2 by bolts, and the bottom of the brim is attached to the strain gauge 3 to measure the output torque by using the deformation of the flexible wheel; the signal line of the strain gauge passes through the notch of the shell end cover and is connected to the signal processing circuit board; the strain gauge is a metal foil strain gauge specially used for measuring torque, and its specific position and quantity can be appropriately increased or decreased according to the corresponding precision compensation algorithm in actual application. The rigid wheel is connected to the output flange 7 and the inner ring 5 of the cross roller bearing by bolts to output power; the wave generator and the input shaft are integrated, and the integrated wave generator and the input shaft 1 are placed in the flexible wheel and driven by the motor to rotate so that the flexible wheel undergoes periodic flexural deformation. The cam of the wave generator is a standard elliptical structure, and the cam of the wave generator is rotatably connected to the inner ring of the cap-shaped flexible wheel through a flexible bearing.

[0042] The present invention also provides the following strain gauge pasting scheme: the strain gauge is a metal foil strain gauge specially used for measuring torque, and each group of strain gauges is a mutually perpendicular strain rosette structure. At least three groups of strain gauges are pasted on the annular surface of the end of the flexspline cap. The three groups of strain gauges are kept at an interval of about 120 degrees in the circumferential position. The long side or short side of the strain gauge is perpendicular to the radial direction of the flexspline.

[0043] like Figure 4 As shown, this embodiment provides a processing circuit for the torque signal of a harmonic reducer, which includes: a half-bridge circuit module, a signal amplification module, a signal superposition module, a filtering module, an ADC signal acquisition module, an EtherCAT slave communication circuit module and a power supply module. The functions of each module are as follows:

[0044] The Wheatstone half-bridge circuit module connects each strain gauge signal derived from the harmonic reducer to the signal processing circuit board and forms a Wheatstone half-bridge circuit with two resistors of the same resistance value to sense the load torque signal and the ripple signal generated by the flexible wheel;

[0045] A signal amplification module, used to amplify the load torque signal and the flexible wheel ripple signal;

[0046] The signal superposition module includes an adjustment resistor and an operational amplifier addition circuit adjusted by a digital potentiometer; the adjustment resistor is used to adjust the signal amplitude so that the peak value of the output signal after vector superposition is minimized; the signal superposition module removes the flexible wheel ripple signal by means of a hardware circuit; the implementation process of the signal superposition module removing the ripple signal by means of a hardware circuit is specifically as follows: when the harmonic reducer is in an unloaded state, one set of strain gauge signals is selected as a reference signal, and then the other two sets of strain gauge signals are used as comparison signals, and the signal gain is adjusted by a high-precision digital potentiometer so that the vector sum after the synthetic vector and the reference signal vector are superimposed is close to zero; the high-precision digital potentiometer is adjusted The gain of the signal is adjusted and the resistance value to be connected when the sum of the three vector superposition is zero is determined; then a resistor with the corresponding resistance value is selected from the resistor standard library as the adjustment resistor; the operational amplifier addition circuit adopts four reverse negative feedback inputs, and the three strain gauge signals are simultaneously connected to the reverse end of the operational amplifier through the corresponding reference resistor or adjustment resistor. The fourth path is to add a bias voltage so that the voltage is in the required range, thereby realizing the removal of the ripple signal through the hardware circuit; once the standard resistance is determined, under load conditions, the signal superposition module can also filter out the ripple signal by itself, and the obtained signal is the required load torque signal, thereby realizing the removal of the ripple signal through the hardware circuit;

[0047] A filtering module, which performs filtering on the signal processed by the signal superposition module;

[0048] The ADC acquisition module performs analog-to-digital conversion on the filtered signal to obtain a digital signal;

[0049] The EtherCAT slave communication module transmits the digital signal obtained by the ADC acquisition module to the next-level EtherCAT slave communication module or the host computer for use as a torque sensor signal; and

[0050] The power supply module provides power to each module, and the power supply module can provide -5 volts, 3.3 volts and 5 volts of power.

[0051] In a preferred embodiment of the present invention, the signal amplification module includes a signal differential input circuit and a signal amplification circuit; the signal differential input circuit ensures the stability of the input signal; and the signal amplification circuit amplifies the signal to the volt level. Figure 5A signal amplification module circuit is an example of an embodiment. The resistance strain gauge signal is differentially input to the module through R6 and R7, and the signal is output from the OUT pin of U1 after front-end processing and signal amplification; R6 and R7 are input resistors, which eliminate the instantaneous voltage pulse of the input signal; C1, C2, C3, and C4 are Y capacitors, which are mainly used to filter out signal differential mode interference; C5 is an X capacitor, which is mainly used to filter out common mode interference; inductor L1 is a common mode inductor, which can filter out high-frequency common mode interference signals; U1 is a precision instrument amplifier, which is used as the core to form a signal amplification circuit; R8 is a gain resistor, which adjusts the signal amplification factor according to the size of the input signal, and C7 is used to stabilize the amplification factor so that the signal is not easy to fluctuate; C6 and C8 are positive and negative power supply filter capacitors of U1; R9 provides a reference and a path for the signal.

[0052] Figure 6 It is a signal superposition module circuit, which adds the amplified signals of the three groups of strain gauge signals to obtain the required torque signal; R10 is a fixed gain resistor that provides a DC bias, which is used to adjust the superimposed signal to a positive level to facilitate subsequent signal acquisition; R11, R12, and R13 are gain adjustment resistors corresponding to the three groups of strain gauge signals, and any one group can be selected as a reference signal resistor. In this embodiment, R11 is selected as the reference signal resistor of the strain gauge amplified signal, and has the same resistance value as the feedback resistor R14, providing a calculation reference for the other two subsequent paths, and then the second and third groups of strain gauge amplified signal gain adjustment resistors, that is, the resistance values ​​of R12 and R13, are adjusted when the harmonic reducer is in the no-load state. The required fixed resistance values ​​of R12 and R13 can be calculated by making corresponding comparisons with the first strain gauge reference signal resistor R11, and resistors of corresponding resistance values ​​are selected from the resistor standard library as R12 and R13 and welded to Figure 6 In the circuit shown. C10 is a feedback capacitor, which increases the smoothness of the signal and makes the signal more stable; R15 provides a reference for the signal and provides a path; R16 is an output resistor, which is connected to the input of the filter module. The op amp addition circuit uses four reverse negative feedback inputs, and connects three signals to the reverse end of the operational amplifier through corresponding resistors at the same time. The fourth path is to add a bias voltage so that the voltage is in the required range, thereby realizing the removal of ripple signals through hardware circuits. Once R11, R12 and R13 are determined, the signal superposition module can also filter out the ripple signal by itself under load conditions, and the resulting signal is the required load torque signal.

[0053] Figure 6The ripple signal filtered by the circuit shown is a low-order ripple signal, especially the periodic ripple signal generated by the harmonic reducer wave generator; if you want to remove higher-order periodic ripple signals, such as the ripple signal generated when the internal and external teeth of the reducer are meshed, five or more sets of strain gauges are required. The hardware circuit processing method is similar to that of three sets of strain gauges, and the method is also to adjust the gain so that the vector sum of the ripple signal is zero. Once the standard resistance is determined, the signal superposition module can also filter out the ripple signal automatically under load conditions, and the resulting signal is the desired load torque signal.

[0054] In a preferred embodiment of the present invention, the filtering module is composed of a tenth-order low-pass filter and a follower; the tenth-order low-pass filter performs low-pass filtering on the previous stage output signal; and the follower is used to increase the output impedance of the circuit. Figure 7 A filter module and follower circuit diagram of an embodiment example is used to perform low-pass filtering on the superimposed signal. Because the signal frequency is low, low-pass filtering is adopted, and the ADC acquisition module is connected after filtering; U3 is a low-pass filter, which adopts a single power supply mode, R16 and R17 are voltage divider resistors, and the reference voltage of the GND pin is obtained by voltage division; C12 and C13 are power supply filter capacitors to ensure the quality of the input voltage; R18 sets the filter frequency, and the required cut-off frequency provides a resistor of appropriate size according to the formula; C11 is connected between the negative input and the ground; R19 is the output resistor, connected to the follower; U4 is an operational amplifier, which is used as a follower here, powered by a single power supply, and increases the input impedance for the subsequent signal to enter the ADC acquisition; R20 provides a reference voltage and a path for the signal; R21 is an output resistor, connected to the subsequent ADC acquisition module.

[0055] In a preferred embodiment of the present invention, the ADC signal acquisition module uses a 24-bit micro-power power frequency suppression ADC to perform analog-to-digital conversion and acquire the signal.

[0056] In a preferred embodiment of the present invention, the EtherCAT slave communication module is communicatively connected with the ADC acquisition module, and transmits the final signal to the next-level EtherCAT slave communication module or the host computer for processing via Ethernet.

[0057] Figure 8a and Figure 8b The two circuits of the power module are shown in Figure 1. Figure 8a It is a part of the circuit of the power module; this part of the circuit is used to convert the positive power signal into a negative power signal and provide a negative reference voltage for the signal amplification module; among them, U5 is a voltage inverter; C14 and C15 are external capacitors of the voltage inverter; C16 and C17 are output signal filter capacitors.

[0058] Figure 8bIt is a part of the circuit of the power module, which is used to convert the 5V power supply into a 3.3V power supply, provide reference voltage for the subsequent ADC acquisition module and power the EtherCat module; U6 provides a fixed output voltage for the LDO linear regulator; C18 and C19 are input filter capacitors; C20 and C21 are output filter capacitors.

[0059] In the present invention, the power module can provide -5V, 3.3V and 5V power to power each module.

[0060] Reference Figure 4 The present invention also provides a method for processing a torque signal of a harmonic reducer, which comprises the following steps:

[0061] 1) Provide a harmonic reducer with torque sensing function, wherein the flexible pulley of the harmonic reducer is a cap-shaped flexible pulley, at least three sets of strain gauges are attached to the bottom of the brim of the cap-shaped flexible pulley to measure the output torque by using the deformation of the flexible pulley; the signal line of the strain gauge passes through the notch of the end cover of the harmonic reducer housing and is connected to the signal processing circuit board; the long side or short side of the strain gauge is perpendicular to the radius direction of the flexible pulley;

[0062] 2) Each set of strain gauge signals is led out from the harmonic flexwheel and connected to the signal processing circuit board and combined with two resistors of the same resistance value to form a Wheatstone half-bridge circuit to sense the load torque signal and the ripple signal generated by the flexwheel;

[0063] The load torque signal and the flexible wheel ripple signal are amplified by the signal amplification module and then enter the signal superposition module; the signal superposition module includes an adjustment resistor adjusted by a digital potentiometer and an operational amplifier addition circuit; the adjustment resistor is used to adjust the signal amplitude so that the output signal peak value after vector superposition is minimized; the signal superposition module removes the ripple signal by means of a hardware circuit;

[0064] The specific implementation process of removing the ripple signal by means of hardware circuit is as follows: when the harmonic reducer is in the no-load state, one set of strain gauge signals is selected as the reference signal, and then the other two sets of strain gauge signals are used as comparison signals. The signal gain is adjusted by a high-precision digital potentiometer so that the vector sum after the synthetic vector and the reference signal vector are superimposed is close to zero; the gain of the signal can be adjusted by a high-precision digital potentiometer to determine the resistance value of the adjustment resistor that should be connected when the sum of the three vector superposition is zero; then a resistor with a corresponding resistance value is selected from the resistor standard library as the adjustment resistor of the signal superposition module; the operational amplifier addition circuit adopts four reverse negative feedback inputs, and the three strain gauge signals are simultaneously connected to the reverse end of the operational amplifier through the corresponding reference resistor or adjustment resistor, and the fourth is to add a bias voltage so that the voltage is in the required range, thereby realizing the removal of the ripple signal by means of hardware circuit; once the standard resistance is determined, under load conditions, the signal superposition module can also filter out the ripple signal by itself, and the resulting signal is the desired load torque signal;

[0065] 3) The remaining signal needs to enter the filtering module for filtering due to the presence of noise; the ADC acquisition module performs analog-to-digital conversion on the collected filtered signal to obtain a digital signal;

[0066] 4) The EtherCAT slave communication module transmits the digital signal to the next-level EtherCAT slave communication module or the host computer for use as a torque sensing signal.

[0067] The present invention adopts a hardware ripple removal method, and the signal can be processed in real time, thereby avoiding the delay problem caused by software processing of the signal. In addition, the requirements for the pasting position and angle of the strain gauge will be greatly reduced. When pasting, the strain gauge only needs to be placed at an approximate position and angle. This can greatly reduce the human influence factors and save the labor cost of pasting the strain gauge, making the installation of the strain gauge simpler and the signal acquisition simpler and more accurate.

[0068] The above-mentioned embodiments only express several implementation methods of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. For ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A method for processing a torque signal of a harmonic reducer, characterized in that: The steps include: 1) Provide a harmonic reducer with torque sensing function, wherein the flexspline of the harmonic reducer is a cap-shaped flexspline, 2N+1 sets of strain gauges are pasted on the bottom of the brim of the cap-shaped flexspline to measure the output torque by using the deformation of the flexspline, where N is an integer greater than or equal to 1; the signal line of the strain gauge passes through the notch of the end cover of the harmonic reducer housing and is connected to a signal processing circuit board; each set of strain gauges is composed of two mutually perpendicular strain gauge units, and the long side or short side of the strain gauge unit is perpendicular to the radius direction of the flexspline; 2) The signals of the two mutually perpendicular strain gauge units are led out from the harmonic flexwheel and then connected to the signal processing circuit board and combined with two resistors of the same resistance value to form a Wheatstone half-bridge circuit to sense the load torque signal and the ripple signal generated by the flexwheel; The load torque signal and the flexible wheel ripple signal are amplified by the signal amplification module and then enter the signal superposition module; the signal superposition module includes an adjustment resistor adjusted by a digital potentiometer and an operational amplifier addition circuit; the adjustment resistor is used to adjust the signal amplitude so that the output signal peak value after vector superposition is minimized; the signal superposition module removes the ripple signal by means of a hardware circuit; The implementation process of removing the ripple signal by means of a hardware circuit is specifically as follows: when the harmonic reducer is in an unloaded state, one set of strain gauge signals is selected as a reference signal, and then the other two sets of strain gauge signals are used as comparison signals, and the signal gain is adjusted by a high-precision digital potentiometer so that the vector sum after the synthetic vector and the reference signal vector are superimposed is close to zero; the resistance value of the adjustment resistor that should be connected when the superposition sum of the three vectors is zero can be determined by adjusting the signal gain by a high-precision digital potentiometer; Then, a resistor with a corresponding resistance value is selected from the resistor standard library as the adjustment resistor of the signal superposition module; the operational amplifier addition circuit adopts four reverse negative feedback inputs, and the three-way strain gauge signal is simultaneously connected to the reverse end of the operational amplifier through the corresponding reference resistor or adjustment resistor. The fourth way is to add a bias voltage so that the voltage is in the required range, thereby realizing the removal of the ripple signal through the hardware circuit; once the standard resistance is determined, under load conditions, the signal superposition module can also filter out the ripple signal by itself, and the obtained signal is the required load torque signal; 3) After removing the ripple signal under no-load conditions, the remaining signal needs to enter the filter module for filtering due to interference from electrical noise or other noise; then the ADC acquisition module performs analog-to-digital conversion on the acquired filtered signal to obtain a digital signal; 4) The EtherCAT slave communication module transmits the digital signal to the next-level EtherCAT slave communication module or the host computer for use as a torque sensing signal.

2. The method for processing the torque signal of a harmonic reducer according to claim 1, characterized in that: The strain gauges are selected into three groups, and the three groups of strain gauges are kept at intervals of 120 degrees in the circumferential position; each group of strain gauges is a strain rosette structure perpendicular to each other.

3. A processing circuit for a harmonic reducer torque signal, characterized in that: include: The Wheatstone half-bridge circuit module connects each set of strain gauge signals from the harmonic reducer to the signal processing circuit board and forms a Wheatstone half-bridge circuit with two resistors of the same resistance value to sense the load torque signal and the ripple signal generated by the flexible wheel; A signal amplification module, used to amplify the load torque signal and the flexible wheel ripple signal; The signal superposition module includes an adjustment resistor and an operational amplifier addition circuit adjusted by a digital potentiometer; the adjustment resistor is used to adjust the signal amplitude so that the peak value of the output signal after vector superposition is minimized; the signal superposition module removes the ripple signal of the flexible wheel by means of a hardware circuit; the implementation process of the signal superposition module removing the ripple signal by means of a hardware circuit is specifically as follows: when the harmonic reducer is in an unloaded state, one set of strain gauge signals is selected as a reference signal, and then the other two sets of strain gauge signals are used as comparison signals, and the signal gain is adjusted by a high-precision digital potentiometer so that the vector sum after the synthetic vector and the reference signal vector are superimposed is close to zero; the high-precision digital potentiometer adjusts the gain of the signal and determines the resistance value that should be connected when the sum of the three vector superpositions is zero; Then, a resistor with a corresponding resistance value is selected from the resistor standard library as an adjustment resistor; the operational amplifier addition circuit adopts four reverse negative feedback inputs, and the three-way strain gauge signal is simultaneously connected to the reverse end of the operational amplifier through the corresponding reference resistor or adjustment resistor. The fourth way is to add a bias voltage so that the voltage is in the required range, thereby realizing the removal of the ripple signal through the hardware circuit; once the standard resistance is determined, under the condition of load, the signal superposition module can also filter out the ripple signal by itself, and the obtained signal is the required load torque signal, thereby realizing the removal of the ripple signal through the hardware circuit; A filtering module, which performs filtering on the signal processed by the signal superposition module; The ADC acquisition module performs analog-to-digital conversion on the filtered signal to obtain a digital signal; The EtherCAT slave communication module transmits the digital signal obtained by the ADC acquisition module to the next-level EtherCAT slave communication module or the host computer for use as a torque sensor signal; as well as The power supply module provides power to each module, and the power supply module can provide -5 volts, 3.3 volts and 5 volts of power.

4. The processing circuit of the torque signal of the harmonic reducer according to claim 3, characterized in that: The signal amplification module comprises a signal differential input circuit and a signal amplification circuit; the signal differential input circuit ensures the stability of the input signal; and the signal amplification circuit amplifies the signal to the volt level.

5. The processing circuit of the torque signal of the harmonic reducer according to claim 3, characterized in that: The operational amplifier adding circuit of the signal superposition module adopts a reverse proportional adder.

6. The processing circuit of the torque signal of the harmonic reducer according to claim 3, characterized in that: The filtering module is composed of a tenth-order low-pass filter and a follower; the tenth-order low-pass filter performs low-pass filtering on the output signal of the previous stage; and the follower is used to increase the output impedance of the circuit.

7. The processing circuit of the torque signal of the harmonic reducer according to claim 3, characterized in that: The ADC acquisition module uses a 24-bit micro-power power frequency suppression ADC to perform analog-to-digital conversion and acquisition on the signal.

8. The processing circuit of the torque signal of the harmonic reducer according to claim 3, characterized in that: The EtherCAT slave communication module is connected to the ADC acquisition module for communication, and transmits the final signal to the next-level EtherCAT slave communication module or the host computer for processing via Ethernet.

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