Sensor for outputting data with reduced noise

Abstract

This sensor is provided with: a substrate having an opening through which an electric cable passes; a sensor circuit that is mounted on the substrate and outputs, in an analog signal format, a sensor signal that is a sensor detection result pertaining to an object; a conductive wire that is wired to the substrate so as to surround the opening; and a processing circuit that is mounted on the substrate and generates a noise-reduced signal in an analog signal format from the difference between the sensor signal and a noise signal that is an electric signal generated in the conductive wire.

Description

Sensors that output noise-reduced data

[0001] The present disclosure relates to sensors that output noise-reduced data.

[0002] Motors used to drive robot arms and motors used to drive machine tools are supplied with drive power by inverters. The inverters are controlled based on PWM (Pulse Width Modulation) signals. The wiring that supplies PWM-controlled motor drive power can be a source of noise.

[0003] JP 2011-176534 A JP 2014-055839 A JP 2008-116782 A JP 2017-034568 A JP 2003-050254 A

[0004] Noise caused by motor drive power has a negative impact on the accuracy of various sensors and the control of various devices. For example, some robot arms are equipped with torque sensors for detecting torque, and noise caused by motor drive power has a negative impact on the accuracy of the torque sensors. Therefore, it is desirable to accurately detect noise and reduce the effect of noise on sensor output.

[0005] According to one aspect of the present disclosure, the sensor comprises a substrate having an opening through which an electrical cable passes, a sensor circuit mounted on the substrate and outputting a sensor signal in the form of an analog signal that is the sensor detection result for an object, conductors wired on the substrate so as to surround the opening, and a processing circuit mounted on the substrate and generating a noise-reduced signal in the form of an analog signal from the difference between the sensor signal and a noise signal that is an electrical signal generated in the conductors.

[0006] 12. FIG. 13 is a diagram illustrating a sensor according to an embodiment of the present disclosure. FIG. 14 is a diagram illustrating a robot including a sensor according to an embodiment of the present disclosure. FIG. 15 is a diagram illustrating noise generated due to motor drive power flowing through an electric cable. FIG. 16 is a waveform diagram illustrating noise reduction processing by a processing circuit in a sensor according to an embodiment of the present disclosure. FIG. 17 is a perspective view showing a board according to a first mode in a sensor according to an embodiment of the present disclosure. FIG. 18 is a perspective view showing a board according to a second mode in a sensor according to an embodiment of the present disclosure. FIG. 19 is a perspective view showing a board according to a third mode in a sensor according to an embodiment of the present disclosure. FIG. 19 is a circuit diagram illustrating the configuration of a processing circuit according to a first mode in a sensor according to an embodiment of the present disclosure. FIG. 19 is a circuit diagram illustrating the configuration of a processing circuit according to a second mode in a sensor according to an embodiment of the present disclosure. FIG. 19 is a circuit diagram illustrating the configuration of a processing circuit according to a third mode in a sensor according to an embodiment of the present disclosure.

[0007] The sensor of the embodiment will be described below with reference to the drawings. In the following description, components having the same or similar functions will be assigned the same reference numerals. Duplicate descriptions of these components may be omitted. The scale of the drawings has been changed as appropriate to facilitate understanding. In the following description, "connected" means "electrically connected."

[0008] <Overall Configuration of Sensor> Fig. 1 is a diagram illustrating a sensor according to an embodiment of the present disclosure, and Fig. 2 is a diagram illustrating a robot equipped with the sensor according to an embodiment of the present disclosure.

[0009] The sensor 1 according to the embodiment of the present disclosure includes a substrate 11, a sensor circuit 12, conductors 13, and a processing circuit 14. Although not shown here, power for driving the sensor 1 is supplied from a battery or a machine in which the sensor 1 is installed.

[0010] The sensor circuit 12 outputs a sensor signal that is the sensor detection result of the object 3 that is the measurement target of the sensor 1. The sensor circuit 12 may be any circuit that outputs a sensor signal that is an analog electrical signal. Examples of sensors 1 that include the sensor circuit 12 include a torque sensor, a current sensor, a voltage sensor, a magnetic sensor, a speed sensor, and a temperature sensor.

[0011] If sensor 1 is a torque sensor, sensor circuit 12 outputs a sensor signal indicative of torque for object 3. If sensor 1 is a current sensor, sensor circuit 12 outputs a sensor signal indicative of current for object 3. If sensor 1 is a voltage sensor, sensor circuit 12 outputs a sensor signal indicative of voltage for object 3. If sensor 1 is a magnetic sensor, sensor circuit 12 outputs a sensor signal indicative of magnetic quantity for object 3. If sensor 1 is a position sensor, sensor circuit 12 outputs a sensor signal indicative of position for object 3. If sensor 1 is a velocity sensor, sensor circuit 12 outputs a sensor signal indicative of velocity for object 3. If sensor 1 is an acceleration sensor, sensor circuit 12 outputs a sensor signal indicative of acceleration for object 3. If sensor 1 is a temperature sensor, sensor circuit 12 outputs a sensor signal indicative of temperature for object 3.

[0012] In the embodiment exemplified below, a case will be described in which the sensor 1 is a torque sensor. The sensor 1 is provided, for example, in the arm of a robot 100. A substrate 11 of the sensor 1 is provided with a sensor circuit 12, conductors 13, a processing circuit 14, and the like.

[0013] The substrate 11 has an opening through which an electric cable passes. The electric cable 2, through which PWM-controlled motor drive power flows, is arranged to pass through the opening. The conductor 13 is wired on the substrate 11 so as to surround the opening of the substrate 11. Thus, the conductor 13 is wired on the substrate 11 so as to surround the electric cable 2, which is a noise generation source resulting from the motor drive power. The conductor 13 may be wired on the surface of the substrate 11 or may be wired inside the substrate 11. The principle of noise signal generation in the conductor 13 will be described later.

[0014] The processing circuit 14 generates a noise-reduced signal in the form of an analog signal or noise-reduced sensor data in the form of a digital signal from the difference between the sensor signal in the form of an analog signal output from the sensor circuit 12 and the noise signal, which is an analog electrical signal generated in the conductor 13. Details of the noise reduction process performed by the processing circuit 14 will be described later.

[0015] The sensor circuit 12 and the processing circuit 14 are mounted on the substrate 11 .

[0016] The sensor 1 includes an arithmetic processing unit (processor). Examples of the arithmetic processing unit include an IC, an LSI, a CPU, an MPU, and a DSP. The arithmetic processing unit includes a sensor circuit 12, a processing circuit 14, and other processing units. Each of these units in the arithmetic processing unit is a functional module implemented by a program executed on the processor. For example, if the sensor circuit 12, the processing circuit 14, and other processing units are implemented in a program format, the functions of each unit can be realized by operating the arithmetic processing unit in accordance with the program. The programs for executing the processes in the sensor circuit 12, the processing circuit 14, and other processing units may be provided in a form recorded on a computer-readable recording medium such as a semiconductor memory, a magnetic recording medium, or an optical recording medium. Alternatively, the sensor circuit 12, the processing circuit 14, and other processing units may be implemented as a semiconductor integrated circuit onto which programs for implementing the functions of each unit are written.

[0017] The sensor 1 also includes at least one memory serving as a storage device. The memory includes the sensor circuit 12, the processing circuit 14, and various storage units within other processing units. Examples of the memory include electrically erasable and recordable nonvolatile memories such as EEPROM (registered trademark), or high-speed read / write random access memories such as DRAM and SRAM. The memory stores programs for operating the sensor circuit 12, the processing circuit 14, and other processing units. The memory also stores various programs and data related to the sensor 1.

[0018] The conductor 13 and its peripheral circuitry may be replaced with a Rogowski coil-type current detection circuit. In this case, the processing circuit 14 is connected to the Rogowski coil-type current detection circuit, and the electric cable 2 is arranged to pass through an opening in the substrate on which the Rogowski coil is provided.

[0019] <Principle of Noise Generation Due to Motor Driving Power> FIG. 3 is a diagram illustrating an example of noise generated due to motor driving power flowing through an electric cable.

[0020] The electric cable 2, which is a wiring that supplies PWM-controlled motor drive power, is a noise source. The motor drive power flowing through the electric cable 2 is a square-wave voltage, and minute changes in the magnetic field occur around the electric cable 2 in response to changes in the square-wave voltage between high and low levels, resulting in noise components being superimposed on the sensor signal output from the sensor circuit 12 located near the electric cable 2. For example, as shown in Figure 3, at time t2 when the motor drive power switches from low to high and at time t4 when the motor drive power switches from high to low, minute changes in the magnetic field occur around the electric cable 2 through which the motor drive power flows. As a result, noise is superimposed on the sensor signal output from the sensor circuit 12 located near the electric cable 2 at times t2 and t4.

[0021] Therefore, in the embodiment of the present disclosure, in order to detect changes in the magnetic field around the electric cable 2 through which the motor drive power flows, a conductor 13 is wired on the substrate 11 so as to surround the electric cable 2 passing through the opening of the substrate 11. In response to changes in the motor drive power flowing through the electric cable 2, a noise signal is generated in the conductor 13.

[0022] <Noise Reduction Processing by Processing Circuit> Figure 4 is a waveform diagram illustrating noise reduction processing by the processing circuit in a sensor according to an embodiment of the present disclosure. From top to bottom, Figure 4 shows the waveforms of a sensor signal, a noise signal, and noise-reduced sensor data. Note that while the noise-reduced sensor data is essentially a digital signal, for ease of understanding, Figure 4 shows it in the form of an analog signal.

[0023] When PWM-controlled motor drive power flows through the electric cable 2 passing through the opening in the substrate 11, minute changes in the magnetic field occur around the electric cable 2, and noise components are superimposed on the sensor signal output from the sensor circuit 12 located near the electric cable 2. Meanwhile, a noise signal corresponding to the minute changes in the magnetic field is generated in the conductor 13 wired on the substrate 11 so as to surround the electric cable 2. By calculating the difference between the noise-superimposed sensor signal output from the sensor circuit 12 and the noise signal generated in the conductor 13 in the processing circuit 14, it is possible to reduce (or remove) the noise component from the sensor signal. In an embodiment of the present disclosure, the signal output from the processing circuit 14 may be a noise-reduced signal in the form of an analog signal, or noise-reduced sensor data in the form of a digital signal.

[0024] <Substrate on which conductors are wired> The substrate of the sensor 1 provided on the arm of the robot 100 may have an opening for passing various cables. The electric cable 2 through which motor drive power flows is also disposed so as to pass through the opening in the substrate. In an embodiment of the present disclosure, the conductors 13 are wired to the substrate 11 of the sensor 1 so as to surround the opening in the substrate 11, so that the conductors 13 surround the electric cable 2. As a variation of this, an opening may be provided in the housing of the sensor 1, the conductors 13 are wired so as to surround the opening in the housing of the sensor 1, and the electric cable 2 is disposed so as to pass through this opening, so that the conductors 13 surround the electric cable 2.

[0025] Some examples of the form of the substrate 11 will be listed below.

[0026] FIG. 5 is a perspective view showing a substrate according to a first form of a sensor according to an embodiment of the present disclosure.

[0027] The substrate 11 according to the first embodiment has a circular ring shape with an opening 50 provided near the center of the disk-shaped substrate. An electric cable 2 passes through the opening 50. On the substrate 11, a conductor 13 wired so as to surround the opening 50, a sensor circuit 12, and a processing circuit 14 are mounted.

[0028] FIG. 6 is a perspective view showing a substrate according to a second embodiment of a sensor according to an embodiment of the present disclosure.

[0029] The substrate 11 according to the second embodiment has a C-shape (an open ring shape) with a notch cut out in the circumferential direction, with an opening 50 provided near the center of the substrate. An electric cable 2 passes through the opening 50. On the substrate 11, a conductor 13 wired in a C-shape so as to surround part of the opening 50, a sensor circuit 12, and a processing circuit 14 are mounted.

[0030] FIG. 7 is a perspective view showing a substrate according to a third embodiment of a sensor according to an embodiment of the present disclosure.

[0031] The substrate 11 according to the third embodiment has a shape in which an opening 50 is provided near the center of the substantially rectangular substrate. An electric cable 2 passes through the opening 50. On the substrate 11, a conductor 13 wired in a substantially rectangular shape so as to surround the opening 50, a sensor circuit 12, and a processing circuit 14 are mounted.

[0032] The first to third forms described above are merely examples, and the substrate may have a substrate shape and wiring shape other than those shown in the drawings, as long as the substrate is wired so that the conductor 13 surrounds the opening 50 through which the electric cable 2 passes.

[0033] <Configuration of Processing Circuit> Several examples of the configuration of the processing circuit 14 will be listed below.

[0034] FIG. 8 is a circuit diagram illustrating the configuration of a processing circuit according to a first mode in a sensor according to an embodiment of the present disclosure.

[0035] The processing circuit 14 is connected to the sensor circuit 12 and the conductors 13. A sensor element (probe) corresponding to the object 3 to be measured by the sensor 1 is connected to terminals P1 and P2 of the sensor circuit 12. For example, if the sensor 1 is a torque sensor, a strain gauge whose resistance value changes depending on the torque applied to the motor is connected to terminals P1 and P2 of the sensor circuit 12. For example, if the sensor 1 is a temperature sensor, a resistance temperature detector is connected to terminals P1 and P2 of the sensor circuit 12.

[0036] The processing circuit 14 according to the first embodiment has a differential amplifier circuit 23. A non-inverting input (+) of the differential amplifier circuit 23 is connected to the subsequent stage of the sensor circuit 12. A conductor 13 wired so as to surround the electric cable 2 is connected to the inverting input (-) of the differential amplifier circuit 23.

[0037] The differential amplifier circuit 23 generates a noise-reduced signal in analog signal format by amplifying the difference signal between the sensor signal output from the sensor circuit 12 and the noise signal generated in the conductor 13. The differential amplifier circuit 23 is configured, for example, by an instrumentation amplifier. The gain of the instrumentation amplifier can be adjusted by adjusting the resistance value, for example.

[0038] An AD converter 24 is connected downstream of the differential amplifier circuit 23. The AD converter 24 converts the noise-reduced signal in analog signal format output from the differential amplifier circuit 23 into noise-reduced sensor data in digital signal format and outputs it.

[0039] The processing circuit 14 according to the first embodiment described with reference to Fig. 8 is suitable for cases where the waveform of the noise component superimposed on the sensor signal and the waveform of the noise signal generated in the conductor 13 have similar waveform shapes and amplitudes. The parameters of the differential amplifier circuit 23 may be set by an operator while checking each waveform using a measuring device such as an oscilloscope, for example, during calibration or performance evaluation before shipping the sensor 1. Alternatively, the parameters that have been set may be readjusted by an operator while checking each waveform using a measuring device such as an oscilloscope during maintenance of the sensor 1.

[0040] FIG. 9 is a circuit diagram illustrating the configuration of a processing circuit according to a second mode in a sensor according to an embodiment of the present disclosure.

[0041] The processing circuit 14 according to the second embodiment is the same as the processing circuit 14 according to the first embodiment described above, except that a first low-pass filter 21 and a second low-pass filter 22 are further provided in front of the differential amplifier circuit 23.

[0042] The processing circuit 14 is connected to the sensor circuit 12 and the conductors 13. A sensor element (probe) corresponding to the object 3 to be measured by the sensor 1 is connected to terminals P1 and P2 of the sensor circuit 12. Examples of the sensor element are as described above in relation to the processing circuit 14 according to the first embodiment.

[0043] The processing circuit 14 according to the second embodiment includes a first low-pass filter 21, a second low-pass filter 22, and a differential amplifier circuit 23.

[0044] A first low-pass filter 21 is connected downstream of the sensor circuit 12. The first low-pass filter 21 generates a first filtered signal by removing high-frequency components from the sensor signal. The parameters of the resistors and capacitors constituting the first low-pass filter 21 may be set to values ​​that can remove high-frequency components compared to the output period of the sensor data from the AD converter 24, for example.

[0045] A second low-pass filter 22 is connected to the conductor 13 that is wired to surround the electric cable 2. The second low-pass filter 22 generates a second filtered signal by removing high-frequency components from the noise signal. The parameters of the resistors and capacitors that make up the second low-pass filter 22 may be set to values ​​that can remove high-frequency components compared to the output period of the sensor data from the AD converter 24, for example.

[0046] The first filtered signal output from the first low-pass filter 21 is input to the non-inverting input (+) of the differential amplifier circuit 23. The second filtered signal output from the second low-pass filter 22 is input to the inverting input (-) of the differential amplifier circuit 23. The differential amplifier circuit 23 generates a noise-reduced signal by amplifying the difference signal between the first filtered signal and the second filtered signal. The differential amplifier circuit 23 is configured, for example, by an instrumentation amplifier. The gain of the instrumentation amplifier can be adjusted, for example, by adjusting the value of resistors.

[0047] An AD converter 24 is connected downstream of the differential amplifier circuit 23. The AD converter 24 converts the noise-reduced signal in analog signal format output from the differential amplifier circuit 23 into noise-reduced sensor data in digital signal format and outputs it.

[0048] The processing circuit 14 according to the second embodiment described with reference to Fig. 9 is suitable for cases where the waveform of the noise component superimposed on the sensor signal and the waveform of the noise signal generated in the conductor 13 have similar waveforms and amplitudes. The parameters of the first low-pass filter 21, the second low-pass filter 22, and the differential amplifier circuit 23 may be set by an operator while checking each waveform using a measuring device such as an oscilloscope, for example, during calibration or performance evaluation before shipping the sensor 1. Alternatively, the parameters may be readjusted once set by an operator while checking each waveform using a measuring device such as an oscilloscope during maintenance of the sensor 1.

[0049] FIG. 10 is a circuit diagram illustrating the configuration of a processing circuit according to a third embodiment in a sensor according to an embodiment of the present disclosure.

[0050] The processing circuit 14 is connected to the sensor circuit 12 and the conductors 13. A sensor element (probe) corresponding to the object 3 to be measured by the sensor 1 is connected to terminals P1 and P2 of the sensor circuit 12. Examples of the sensor element are as described above in relation to the processing circuit 14 according to the first embodiment.

[0051] The processing circuit 14 according to the third embodiment has a differential input AD converter 35. The non-inverting input (+) of the differential input AD converter 35 is connected to the subsequent stage of the sensor circuit 12. The conductor 13, which is wired so as to surround the electric cable 2, is connected to the inverting input (-) of the differential input AD converter 35.

[0052] The differential input AD converter 35 generates a differential signal between the sensor signal in analog signal format and the noise signal in analog signal format, and converts this differential signal into noise-reduced sensor data in digital signal format and outputs it.

[0053] The processing circuit 14 according to the third embodiment described with reference to Fig. 10 is suitable for cases where the waveform of the noise component superimposed on the sensor signal and the waveform of the noise signal generated in the conductor 13 have similar waveform shapes and amplitudes. The parameters of the differential input AD converter 35 may be set by an operator while checking each waveform using a measuring device such as an oscilloscope, for example, during calibration or performance evaluation before shipping the sensor 1. Alternatively, the parameters that have been set may be readjusted by an operator while checking each waveform using a measuring device such as an oscilloscope during maintenance of the sensor 1.

[0054] FIG. 11 is a circuit diagram illustrating the configuration of a processing circuit according to a fourth mode in a sensor according to an embodiment of the present disclosure.

[0055] The processing circuit 14 is connected to the sensor circuit 12 and the conductors 13. A sensor element (probe) corresponding to the object 3 to be measured by the sensor 1 is connected to terminals P1 and P2 of the sensor circuit 12. Examples of the sensor element are as described above in relation to the processing circuit 14 according to the first embodiment.

[0056] The processing circuit 14 in the second form has a first low-pass filter 31, a second low-pass filter 32, a first voltage follower 36, a second voltage follower 37, a first amplifier circuit 33, a second amplifier circuit 34, and a differential input AD converter 35.

[0057] A first low-pass filter 31 is connected downstream of the sensor circuit 12. The first low-pass filter 31 generates a first filtered signal by removing high-frequency components from the sensor signal. The parameters of the resistors and capacitors constituting the first low-pass filter 31 may be set to values ​​that can remove high-frequency components compared to the output period of the sensor data from the differential input AD converter 35, for example.

[0058] A first voltage follower 36 is connected to the rear stage of the first low-pass filter 31. The first voltage follower 36 has the function of increasing the input impedance of the non-inverting input (+) of the first voltage follower 36 as seen from the sensor circuit 12. By providing the first voltage follower 36, it is possible to prevent a large current from flowing from the sensor circuit 12 into the first amplifier circuit 33, thereby suppressing sensor errors.

[0059] The first amplifier circuit 33 is connected to the subsequent stage of the first voltage follower 36. The first amplifier circuit 33 amplifies the first filtered signal to generate a first amplified signal.

[0060] A second low-pass filter 32 is connected to the conductor 13 that is wired to surround the electric cable 2. The second low-pass filter 32 generates a second filtered signal by removing high-frequency components from the noise signal. The parameters of the resistors and capacitors that make up the second low-pass filter 32 may be set to values ​​that can remove high-frequency components compared to the output period of the sensor data from the differential input AD converter 35, for example.

[0061] A second voltage follower 37 is connected downstream of the second low-pass filter 32. In order to make the waveform of the noise component superimposed on the sensor signal and the waveform of the noise signal as similar as possible, the second voltage follower 37 is provided on the wiring through which the noise signal flows, corresponding to the first voltage follower 36 provided on the wiring through which the sensor signal flows.

[0062] The second amplifier circuit 34 is connected to the subsequent stage of the second voltage follower 37. The second amplifier circuit 34 amplifies the second filtered signal to generate a second amplified signal.

[0063] The first amplified signal output from the first amplifier circuit 33 is input to a non-inverting input (+) of the differential input AD converter 35. The second amplified signal output from the second amplifier circuit 34 is input to an inverting input (-) of the differential input AD converter 35. The differential input AD converter 35 generates a differential signal between the first amplified signal in analog signal format and the second amplified signal in analog signal format, and converts this differential signal into noise-reduced sensor data in digital signal format and outputs it.

[0064] The processing circuit 14 according to the fourth embodiment described with reference to FIG. 11 is suitable for cases where the waveform of the noise component superimposed on the sensor signal and the waveform of the noise signal generated in the conductor 13 have similar waveforms but a large difference in amplitude. The resistance values ​​of the resistors and variable resistors of the first amplifier circuit 33 and the second amplifier circuit 34 are adjusted in advance so that the amplitude of the noise component superimposed on the sensor signal and the amplitude of the noise signal are similar. The parameters of the first low-pass filter 31, the second low-pass filter 32, the first voltage follower 36, the second voltage follower 37, the first amplifier circuit 33, and the second amplifier circuit 34 may be set by an operator while checking the waveforms using a measuring device such as an oscilloscope, for example, during calibration or performance evaluation before shipment of the sensor 1. Alternatively, the parameters may be readjusted by an operator while checking the waveforms using a measuring device such as an oscilloscope during maintenance of the sensor 1.

[0065] Fig. 12 is a circuit diagram illustrating the configuration of a processing circuit according to a fifth embodiment of the sensor according to the present disclosure. Fig. 13 is a diagram illustrating waveforms of various components in the processing circuit according to the fifth embodiment shown in Fig. 12. From top to bottom, Fig. 13 shows the waveforms of the amplified signal output from amplifier circuit 42, the noise signal generated in conductor 13, the adjusted signal output from adjustment circuit 43, and the noise-reduced sensor data output from differential input AD converter 44. Note that while the noise-reduced sensor data is essentially a digital signal, for ease of understanding, Fig. 13 shows it in the form of an analog signal.

[0066] The processing circuit 14 is connected to the sensor circuit 12 and the conductors 13. A sensor element (probe) corresponding to the object 3 to be measured by the sensor 1 is connected to terminals P1 and P2 of the sensor circuit 12. Examples of the sensor element are as described above in relation to the processing circuit 14 according to the first embodiment.

[0067] The processing circuit 14 according to the third embodiment includes a low-pass filter 41 , a voltage follower 45 , an amplifier circuit 42 , an adjustment circuit 43 , and a differential input AD converter 44 .

[0068] A low-pass filter 41 is connected downstream of the sensor circuit 12. The low-pass filter 41 generates a filtered signal by removing high-frequency components from the sensor signal. The parameters of the resistors and capacitors that make up the low-pass filter 41 may be set to values ​​that can remove high-frequency components compared to the output period of the sensor data from the differential input AD converter 44. The low-pass filter 41 may be omitted.

[0069] A voltage follower 45 is connected downstream of the low-pass filter 41. The voltage follower 45 has the function of increasing the input impedance of the non-inverting input (+) of the voltage follower 45 as seen from the sensor circuit 12. By providing the voltage follower 45, it is possible to prevent a large current from flowing from the sensor circuit 12 into the amplifier circuit 42, thereby suppressing sensor errors.

[0070] The amplifier circuit 42 is connected to the subsequent stage of the voltage follower 45. The amplifier circuit 42 amplifies the filtered signal to generate an amplified signal.

[0071] An adjustment circuit 43 is connected to the conductor 13 that is wired to surround the electric cable 2. The adjustment circuit 43 adjusts the amplitude of a specific frequency component of a noise signal generated in the conductor 13 and adjusts the phase of the noise signal to generate and output an adjusted signal. The adjustment circuit 43 is provided so that the sensor 1 can be used even when the waveform of the noise component superimposed on the sensor signal and the waveform of the noise signal generated in the conductor 13 are significantly different. The adjustment circuit 43 adjusts the amplitude and phase of a specific frequency component of the noise signal so that the waveform of the noise component superimposed on the sensor signal and the waveform of the noise signal generated in the conductor 13 have approximately the same waveform. The adjustment circuit 43 is configured, for example, by appropriately combining a differentiation circuit, an integration circuit, and a band-pass filter.

[0072] The amplified signal output from the amplifier circuit 42 is input to the non-inverting input (+) of the differential input AD converter 44. The conditioned signal output from the conditioning circuit 43 is input to the inverting input (-) of the differential input AD converter 44. The differential input AD converter 44 generates a differential signal between the amplified signal in analog signal format and the conditioned signal in analog signal format, and converts this differential signal into noise-reduced sensor data in digital signal format for output.

[0073] The processing circuit 14 according to the fifth embodiment described with reference to Figures 12 and 13 is suitable for cases where the waveform of the noise component superimposed on the sensor signal is significantly different from the waveform of the noise signal generated in the conductor 13. For example, if the sensor signal output from the sensor circuit 12 is an analog signal indicating the voltage applied to a capacitance, the capacitance is a physical quantity related to the electric field, while the noise signal is strongly related to the magnetic field. Therefore, the waveforms of the noise component superimposed on the sensor signal and the noise signal generated in the conductor 13 are significantly different in phase and frequency. In the processing circuit 14 according to the third embodiment, the parameters of the amplifier circuit 42 and the adjustment circuit 43 are adjusted in advance so that the amplitude of the noise component superimposed on the sensor signal is approximately the same as the amplitude of the noise signal. The parameters of the low-pass filter 41, the voltage follower 45, the amplifier circuit 42, and the adjustment circuit 43 can be set by an operator while checking the waveforms using a measuring device such as an oscilloscope, for example, during calibration or performance evaluation of the sensor 1 before shipment. Alternatively, once the parameters have been set, they may be readjusted by an operator during maintenance of the sensor 1 while checking the waveforms using a measuring device such as an oscilloscope.

[0074] FIG. 14 is a circuit diagram illustrating the configuration of a processing circuit according to a sixth embodiment in a sensor according to an embodiment of the present disclosure.

[0075] The processing circuit 14 is connected to the sensor circuit 12 and the conductors 13. A sensor element (probe) corresponding to the object 3 to be measured by the sensor 1 is connected to terminals P1 and P2 of the sensor circuit 12. Examples of the sensor element are as described above in relation to the processing circuit 14 according to the first embodiment.

[0076] The processing circuit 14 according to the sixth embodiment has a first AD converter 53 , a second AD converter 54 , and a differential operation circuit 55 .

[0077] A first AD converter 53 is connected to the rear stage of the sensor circuit 12. The first AD converter 53 converts the sensor signal in an analog signal format into first digital data in a digital signal format.

[0078] The conductor 13, which is wired to surround the electric cable 2, is connected to the second AD converter 54. The second AD converter 54 converts the noise signal in the analog signal format generated in the conductor 13 into second digital data in the digital signal format.

[0079] A differential operation circuit 55 is connected downstream of the first AD converter 53 and the second AD converter 54. The differential operation circuit 55 generates first amplified digital data by amplifying the first digital data through digital operation processing. The differential operation circuit 55 also generates second amplified digital data by amplifying the second digital data through digital operation processing, or generates adjusted digital data by adjusting the amplitude of a specific frequency component of the second digital data through digital filter processing and adjusting the phase of the second digital data through digital operation processing. The differential operation circuit 55 performs digital operation processing to generate noise-reduced sensor data by calculating the difference between the first amplified digital data and the second amplified digital data, or the difference between the first amplified digital data and the adjusted digital data. The differential operation circuit 55 is configured, for example, with an IC, an LSI, a CPU, an MPU, a DSP, or the like.

[0080] The processing circuit 14 according to the sixth embodiment described with reference to Fig. 14 is suitable for cases where the calculation speed of the differential calculation circuit 55 is sufficiently fast compared with the main frequency components contained in the waveforms of the sensor signal and the noise signal. The parameters of the first AD converter 53, the second AD converter 54, and the differential calculation circuit 55 may be set by an operator while checking each waveform using a measuring device such as an oscilloscope, for example, during calibration or performance evaluation before shipping the sensor 1. Alternatively, the parameters may be readjusted once set by an operator while checking each waveform using a measuring device such as an oscilloscope during maintenance of the sensor 1.

[0081] FIG. 15 is a circuit diagram illustrating the configuration of a processing circuit according to the seventh mode in a sensor according to an embodiment of the present disclosure.

[0082] The processing circuit 14 according to the seventh embodiment is the processing circuit 14 according to the sixth embodiment described above, further comprising a first low-pass filter 51 and a second low-pass filter 52 in the stage preceding the differential operation circuit 55.

[0083] The processing circuit 14 is connected to the sensor circuit 12 and the conductors 13. A sensor element (probe) corresponding to the object 3 to be measured by the sensor 1 is connected to terminals P1 and P2 of the sensor circuit 12. Examples of the sensor element are as described above in relation to the processing circuit 14 according to the first embodiment.

[0084] The processing circuit 14 according to the seventh embodiment has a first low-pass filter 51 , a second low-pass filter 52 , a first AD converter 53 , a second AD converter 54 , and a differential operation circuit 55 .

[0085] A first low-pass filter 51 is connected downstream of the sensor circuit 12. The first low-pass filter 51 generates a first filtered signal by removing high-frequency components from the sensor signal. The parameters of the resistors and capacitors constituting the first low-pass filter 51 may be set to values ​​that can remove high-frequency components compared to the output period of the sensor data from the first AD converter 53, for example.

[0086] A second low-pass filter 52 is connected to the conductor 13 that is wired to surround the electric cable 2. The second low-pass filter 52 generates a second filtered signal by removing high-frequency components from the noise signal. The parameters of the resistors and capacitors that make up the second low-pass filter 52 may be set to values ​​that can remove high-frequency components compared to the output period of the sensor data from the second AD converter 54, for example.

[0087] The first AD converter 53 receives the first filtered signal output from the first low-pass filter 51. The first AD converter 53 converts the first filtered signal in analog signal format into first filtered digital data in digital signal format.

[0088] The second AD converter 54 receives the second filtered signal output from the second low-pass filter 52. The second AD converter 54 converts the second filtered signal in the form of an analog signal into second filtered digital data in the form of a digital signal.

[0089] A differential operation circuit 55 is connected downstream of the first AD converter 53 and the second AD converter 54. The differential operation circuit 55 generates first amplified digital data by amplifying the first filtered digital data through digital operation processing. The differential operation circuit 55 also generates second amplified digital data by amplifying the second filtered digital data through digital operation processing, or generates adjusted digital data by adjusting the amplitude of a specific frequency component of the second filtered digital data through digital filtering processing and adjusting the phase of the second filtered digital data through digital operation processing. The differential operation circuit 55 performs digital operation processing to generate noise-reduced sensor data by calculating the difference between the first amplified digital data and the second amplified digital data, or the difference between the first amplified digital data and the adjusted digital data. The differential operation circuit 55 is configured, for example, with an IC, an LSI, a CPU, an MPU, a DSP, or the like.

[0090] The processing circuit 14 according to the seventh embodiment described with reference to Fig. 15 is suitable for cases where the calculation speed of the differential calculation circuit 55 is sufficiently fast compared to the main frequency components contained in the waveforms of the sensor signal and the noise signal. The parameters of the first low-pass filter 51, the second low-pass filter 52, the first AD converter 53, the second AD converter 54, and the differential calculation circuit 55 may be set by an operator while checking each waveform using a measuring device such as an oscilloscope, for example, during calibration or performance evaluation before shipping the sensor 1. Alternatively, the parameters may be readjusted once set by an operator while checking each waveform using a measuring device such as an oscilloscope during maintenance of the sensor 1.

[0091] Advantages of the Embodiments of the Present Disclosure According to the embodiments of the present disclosure, noise can be accurately detected and the influence of noise on the sensor output can be reduced.

[0092] Generally, PWM-controlled motor drive power switches between high and low states at high speeds, making sensor data from sensors located around the electric cable through which the motor drive power flows susceptible to noise. Conventional approaches, such as averaging sensor data over time, have been used to reduce the impact of noise on sensor output, but this approach has the drawback of reducing the speed of sensor processing. Furthermore, robots and machine tools often perform complex movements, and the loads on the robots and machine tools vary. Therefore, the waveform of the motor drive power flowing through the electric cable in the robot or machine tool varies significantly and is difficult to reproduce. In contrast, according to an embodiment of the present disclosure, a conductor wired around the electric cable can accurately detect noise signals resulting from changes in the motor drive power flowing through the electric cable. By canceling out the noise component of the sensor signal output from the sensor circuit with the noise signal detected by the conductor wire, sensor data with reduced noise impact is generated, ensuring high-speed and accurate sensor processing.

[0093] For example, the substrate of a sensor mounted on a robot arm may have an opening for passing various cables. Generally, when mounting components or wiring on a substrate, the presence of an opening in the substrate often limits the component placement and wiring pattern. In contrast, in an embodiment of the present disclosure, noise signals can be detected simply by wiring conductors around the opening in the sensor substrate, thereby avoiding an increase in the size of the sensor due to the implementation of a circuit for detecting noise signals.

[0094] Although the present disclosure has been described in detail above, the present disclosure is not limited to the individual embodiments and individual variations described above. Various additions, substitutions, modifications, partial deletions, etc. are possible for these embodiments and variations within the scope of the gist of the present disclosure, or within the scope of the gist of the present disclosure derived from the content of the claims and their equivalents. These embodiments and variations can also be implemented in combination. For example, in the above-described embodiments and variations, the order of each operation and the order of each process are shown as examples and are not limited to these. The same applies when numerical values ​​or mathematical formulas are used in the description of the above-described embodiments and variations.

[0095] <Supplementary Notes> The following supplementary notes are further disclosed regarding the above-described embodiment and modifications.

[0096] (Supplementary Note 1) A sensor comprising: a substrate having an opening through which an electric cable passes; a sensor circuit mounted on the substrate and outputting a sensor signal in analog signal format that is the sensor detection result of an object; conductors wired on the substrate so as to surround the opening; and a processing circuit mounted on the substrate and generating a noise-reduced signal in analog signal format from the difference between the sensor signal and a noise signal that is an electric signal generated in the conductors. (Supplementary Note 2) The sensor according to Supplementary Note 1, wherein the processing circuit has a differential amplifier circuit that generates the noise-reduced signal by amplifying the difference signal between the sensor signal and the noise signal. (Supplementary Note 3) The sensor according to Supplementary Note 2, further comprising an AD converter that converts the noise-reduced signal in analog signal format output from the differential amplifier circuit into noise-reduced sensor data in digital signal format. (Supplementary Note 4) The sensor according to Supplementary Note 1, wherein the processing circuit has: a first low-pass filter that generates a first filtered signal by removing high-frequency components from the sensor signal, a second low-pass filter that generates a second filtered signal by removing high-frequency components from the noise signal, and a differential amplifier circuit that generates a noise-reduced signal by amplifying a difference signal between the first filtered signal output from the first low-pass filter and the second filtered signal output from the second low-pass filter. (Supplementary Note 5) The sensor according to Supplementary Note 4, further comprising an AD converter that converts the noise-reduced signal in analog signal form output from the differential amplifier circuit into noise-reduced sensor data in digital signal form. (Supplementary Note 6) A sensor comprising: a substrate having an opening through which an electric cable passes; a sensor circuit mounted on the substrate and outputting a sensor signal in an analog signal format that is the sensor detection result for an object; conductors wired on the substrate so as to surround the opening; and a processing circuit mounted on the substrate and generating noise-reduced sensor data in a digital signal format from the difference between the sensor signal and a noise signal that is an electric signal generated in the conductors.(Supplementary Note 7) The sensor according to Supplementary Note 6, wherein the processing circuit has a differential input AD converter that generates a differential signal between the sensor signal in analog signal form and the noise signal in analog signal form, and converts the differential signal into noise-reduced sensor data in digital signal form. (Supplementary Note 8) The sensor according to Supplementary Note 6, wherein the processing circuit has: a first low-pass filter that generates a first filtered signal by removing high-frequency components from the sensor signal, a second low-pass filter that generates a second filtered signal by removing high-frequency components from the noise signal, a first amplifier circuit that generates a first amplified signal by amplifying the first filtered signal output from the first low-pass filter, a second amplifier circuit that generates a second amplified signal by amplifying the second filtered signal output from the second low-pass filter, and a differential input AD converter that generates a differential signal between the first amplified signal in analog signal form output from the first amplifier circuit and the second amplified signal in analog signal form output from the second amplifier circuit, and converts the differential signal into noise-reduced sensor data in digital signal form. (Supplementary Note 9) The sensor according to Supplementary Note 6, wherein the processing circuit comprises: a low-pass filter that generates a filtered signal by removing high frequency components from the sensor signal; an amplifier circuit that generates an amplified signal by amplifying the filtered signal output from the low-pass filter; an adjustment circuit that adjusts the phase and the amplitude of specific frequency components of the noise signal and outputs the adjusted signal; and a differential input AD converter that generates a difference signal between the amplified signal in analog signal form output from the amplifier circuit and the adjusted signal in analog signal form output from the adjustment circuit, and converts the difference signal into noise-reduced sensor data in digital signal form.(Supplementary Note 10) The sensor according to Supplementary Note 6, wherein the processing circuit has: a first AD converter that converts the sensor signal in analog signal format into first digital data in digital signal format, a second AD converter that converts the noise signal in analog signal format into second digital data in digital signal format, and a differential operation circuit that generates noise-reduced sensor data by taking the difference between first amplified digital data obtained by amplifying the first digital data and second amplified digital data obtained by amplifying the second digital data. (Supplementary Note 11) The sensor according to Supplementary Note 6, wherein the processing circuit has: a first AD converter that converts the sensor signal in analog signal format into first digital data in digital signal format, a second AD converter that converts the noise signal in analog signal format into second digital data in digital signal format, and a differential operation circuit that generates noise-reduced sensor data by taking the difference between first amplified digital data obtained by amplifying the first digital data and adjusted digital data obtained by adjusting the phase and the amplitude of a specific frequency component of the second digital data. (Supplementary Note 12) The sensor according to Supplementary Note 6, wherein the processing circuit comprises: a first low-pass filter that generates a first filtered signal by removing high-frequency components from the sensor signal; a second low-pass filter that generates a second filtered signal by removing high-frequency components from the noise signal; a first AD converter that converts the first filtered signal in analog signal format output from the first low-pass filter into first filtered digital data in digital signal format; a second AD converter that converts the second filtered signal in analog signal format output from the second low-pass filter into second filtered digital data in digital signal format; and a differential operation circuit that generates noise-reduced sensor data by taking the difference between the first filtered digital data and the second filtered digital data.(Supplementary Note 13) The sensor according to Supplementary Note 6, wherein the processing circuit comprises: a first low-pass filter that generates a first filtered signal by removing high-frequency components from the sensor signal; a second low-pass filter that generates a second filtered signal by removing high-frequency components from a noise signal; a first AD converter that converts the first filtered signal in an analog signal format output from the first low-pass filter into first filtered digital data in a digital signal format; a second AD converter that converts the second filtered signal in an analog signal format output from the second low-pass filter into second filtered digital data in a digital signal format; and a differential operation circuit that generates noise-reduced sensor data by taking the difference between first amplified digital data obtained by amplifying the first filtered digital data and adjusted digital data obtained by adjusting the phase and the amplitude of a specific frequency component of the second filtered digital data. (Supplementary Note 14) The sensor according to any one of Supplementary Notes 1 to 13, wherein the sensor circuit outputs any of a sensor signal indicating torque for the object, a sensor signal indicating current for the object, a sensor signal indicating voltage for the object, a sensor signal indicating magnetic quantity for the object, a sensor signal indicating any of position, velocity, and acceleration for the object, and a sensor signal indicating temperature for the object.

[0097] REFERENCE SIGNS LIST 1 sensor 2 electric cable 3 object 11 substrate 12 sensor circuit 13 conducting wire 14 processing circuit 21 first low-pass filter 22 second low-pass filter 23 differential amplifier circuit 24 AD converter 31 first low-pass filter 32 second low-pass filter 33 first amplifier circuit 34 second amplifier circuit 35 differential input AD converter 36 first voltage follower 37 second voltage follower 41 low-pass filter 42 amplifier circuit 43 adjustment circuit 44 differential input AD converter 45 voltage follower 50 opening 51 first low-pass filter 52 second low-pass filter 53 first AD converter 54 second AD converter 55 differential calculation circuit

Claims

1. A sensor comprising: a substrate having an opening through which an electric cable passes; a sensor circuit mounted on the substrate and outputting a sensor signal in analog signal format that is the sensor detection result for an object; conductors wired on the substrate so as to surround the opening; and a processing circuit mounted on the substrate and generating a noise-reduced signal in analog signal format from the difference between the sensor signal and a noise signal that is an electric signal generated in the conductors.

2. The sensor of claim 1, wherein the processing circuitry includes a differential amplifier circuit that generates the noise-reduced signal by amplifying a difference signal between the sensor signal and the noise signal.

3. The sensor according to claim 2, further comprising an AD converter that converts the noise-reduced signal in analog signal format output from the differential amplifier circuit into the noise-reduced sensor data in digital signal format.

4. The sensor of claim 1, wherein the processing circuit comprises: a first low-pass filter that generates a first filtered signal by removing high-frequency components from the sensor signal; a second low-pass filter that generates a second filtered signal by removing high-frequency components from the noise signal; and a differential amplifier circuit that generates the noise-reduced signal by amplifying a difference signal between the first filtered signal output from the first low-pass filter and the second filtered signal output from the second low-pass filter.

5. The sensor according to claim 4, further comprising an AD converter that converts the noise-reduced signal in analog signal format output from the differential amplifier circuit into the noise-reduced sensor data in digital signal format.

6. A sensor comprising: a substrate having an opening through which an electric cable passes; a sensor circuit mounted on the substrate and outputting a sensor signal in analog signal format which is the sensor detection result for an object; conductors wired on the substrate so as to surround the opening; and a processing circuit mounted on the substrate and generating noise-reduced sensor data in digital signal format from the difference between the sensor signal and a noise signal which is an electric signal generated in the conductors.

7. The sensor of claim 6, wherein the processing circuitry includes a differential input AD converter that generates a differential signal between the sensor signal in analog signal form and the noise signal in analog signal form, and converts the differential signal into the noise-reduced sensor data in digital signal form.

8. The sensor of claim 6, wherein the processing circuit comprises: a first low-pass filter that generates a first filtered signal by removing high frequency components from the sensor signal; a second low-pass filter that generates a second filtered signal by removing high frequency components from the noise signal; a first amplifier circuit that generates a first amplified signal by amplifying the first filtered signal output from the first low-pass filter; a second amplifier circuit that generates a second amplified signal by amplifying the second filtered signal output from the second low-pass filter; and a differential input AD converter that generates a difference signal between the first amplified signal in analog signal form output from the first amplifier circuit and the second amplified signal in analog signal form output from the second amplifier circuit, and converts the difference signal into the noise-reduced sensor data in digital signal form.

9. The sensor according to claim 6, wherein the processing circuit comprises: a low-pass filter that generates a filtered signal by removing high frequency components from the sensor signal; an amplifier circuit that generates an amplified signal by amplifying the filtered signal output from the low-pass filter; an adjustment circuit that adjusts the phase of the noise signal and the amplitude of specific frequency components and outputs an adjusted signal; and a differential input AD converter that generates a difference signal between the amplified signal in the analog signal format output from the amplifier circuit and the conditioned signal in the analog signal format output from the adjustment circuit, and converts the difference signal into the noise-reduced sensor data in the digital signal format.

10. The sensor according to claim 6, wherein the processing circuit comprises: a first AD converter that converts the sensor signal in analog signal format into first digital data in digital signal format; a second AD converter that converts the noise signal in analog signal format into second digital data in digital signal format; and a differential operation circuit that generates the noise-reduced sensor data by taking the difference between first amplified digital data obtained by amplifying the first digital data and second amplified digital data obtained by amplifying the second digital data.

11. The sensor according to claim 6, wherein the processing circuit comprises: a first AD converter that converts the sensor signal in analog signal format into first digital data in digital signal format; a second AD converter that converts the noise signal in analog signal format into second digital data in digital signal format; and a differential operation circuit that generates the noise-reduced sensor data by taking the difference between first amplified digital data obtained by amplifying the first digital data and adjusted digital data obtained by adjusting the phase and the amplitude of a specific frequency component of the second digital data.

12. The sensor according to claim 6, wherein the processing circuit comprises: a first low-pass filter that generates a first filtered signal by removing high-frequency components from the sensor signal; a second low-pass filter that generates a second filtered signal by removing high-frequency components from the noise signal; a first AD converter that converts the first filtered signal in analog signal format output from the first low-pass filter into first filtered digital data in digital signal format; a second AD converter that converts the second filtered signal in analog signal format output from the second low-pass filter into second filtered digital data in digital signal format; and a differential operation circuit that generates the noise-reduced sensor data by taking the difference between first amplified digital data obtained by amplifying the first filtered digital data and second amplified digital data obtained by amplifying the second filtered digital data.

13. The sensor according to claim 6, wherein the processing circuit comprises: a first low-pass filter that generates a first filtered signal by removing high-frequency components from the sensor signal; a second low-pass filter that generates a second filtered signal by removing high-frequency components from the noise signal; a first AD converter that converts the first filtered signal in analog signal format output from the first low-pass filter into first filtered digital data in digital signal format; a second AD converter that converts the second filtered signal in analog signal format output from the second low-pass filter into second filtered digital data in digital signal format; and a differential operation circuit that generates the noise-reduced sensor data by taking the difference between first amplified digital data obtained by amplifying the first filtered digital data and adjusted digital data obtained by adjusting the phase and the amplitude of a specific frequency component of the second filtered digital data.

14. The sensor according to any one of claims 1 to 13, wherein the sensor circuit outputs any of the sensor signals indicating torque for the object, the sensor signal indicating current for the object, the sensor signal indicating voltage for the object, the sensor signal indicating magnetic quantity for the object, the sensor signal indicating any of position, velocity, and acceleration for the object, and the sensor signal indicating temperature for the object.

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