Variable speed drive and torque sensor

Abstract

Examples include a method for controlling a variable speed drive of an electric motor. The variable speed drive is connected to a torque sensor for sensing a torque provided by the electric motor. The method includes executing a predetermined torque sequence by the electric motor. The method also includes measuring, by the torque sensor, a measured torque sequence corresponding to the predetermined torque sequence, and comparing the predetermined torque sequence and the measured torque sequence. As a result of the comparison, one or more torque sensor transfer function parameters are determined.

Description

Technical Field

[0001] The present invention relates to a method for controlling an electric motor (e.g., an asynchronous electric motor) using a variable speed drive, and to a variable speed drive for implementing the method. Background Technology

[0002] In conventional variable-speed drives for electric motors, especially asynchronous types, the control laws are executed by a processing unit that receives an input reference. Based on this input reference and measurements taken on the motor, the processing unit determines the voltage reference to be applied to the electric motor. Based on this voltage reference, the processing unit determines the control voltage to be applied to each output phase connected to the motor. These voltages are then applied to the motor using an electronic power supply architecture.

[0003] In some cases, value measurements on a motor include torque measurements, which are obtained by a torque sensor. While static torque measurements can be reliably obtained using a torque sensor, reliable measurements of dynamic torque are more difficult to achieve. In some variable-speed drives for electric motors, a reliable torque measurement can be obtained approximately 1 second after a given torque is applied. Applying a given torque allows the desired acceleration to be achieved, corresponding to an input reference received by the processing unit of a conventional variable-speed drive. Accurate measurement of the torque value thus helps to precisely achieve the desired acceleration. For example, when controlling a motor, the lack of dynamics in torque measurement limits reliance on torque measurements, resulting in slow correction of static errors.

[0004] The purpose of this invention is to propose a control method for a variable speed drive for controlling an electric motor, which allows for increased torque accuracy during transition phases, particularly allowing for increased control gain to achieve improved dynamic torque, while limiting dependence on torque sensor characteristics, so as to achieve the desired performance of the electric motor accurately and quickly. Summary of the Invention

[0005] This invention is defined by the appended independent claims. Additional features and advantages of the concepts disclosed herein are set forth in the following description.

[0006] This disclosure describes a method for controlling a variable speed drive for an electric motor, the variable speed drive being connected to a torque sensor for sensing torque provided by the electric motor, the method comprising:

[0007] - A predetermined torque sequence is executed by an electric motor;

[0008] - A measured torque sequence corresponding to a predetermined torque sequence is measured by a torque sensor;

[0009] - Compare the predetermined torque sequence with the measured torque sequence; and

[0010] - As a result of the comparison, determine the transfer function parameters of one or more torque sensors.

[0011] This method allows for increased accuracy in torque measurement, taking into account measurement delay and sampling time, thereby increasing the accuracy of the transmission drive, particularly by allowing dynamic torque measurement.

[0012] Optionally, one or more torque sensor transfer function parameters include one or more of a delay parameter, a gain parameter, or a bandwidth parameter. Each such parameter contributes to describing the behavior of the torque sensor or electric motor, and this behavior is encoded into the torque sensor transfer function parameters.

[0013] Optionally, the predetermined torque sequence includes one or more torque steps. Torque steps can, for example, provide information about gain or delay parameters. Repeated torque steps can improve the accuracy of determining the torque sensor transfer function parameters.

[0014] Optionally, the predetermined torque sequence includes chirped torque oscillations. These chirped torque oscillations can, for example, provide information about bandwidth parameters.

[0015] Optionally, the predetermined torque sequence includes one or more torque steps followed by chirped torque oscillations. This predetermined torque sequence configuration can, for example, allow the determination of multiple parameters, including delay parameters, gain parameters, and bandwidth parameters. In some cases, one or more torque steps are at a first torque amplitude, and the chirped torque oscillations are at a second torque amplitude, which is lower than the first torque amplitude. Using different amplitudes in this way helps to determine specific parameters based on the behavior of the torque sensor or electric motor; for example, using higher amplitudes to determine gain and delay behavior and related parameters, while using lower amplitudes to determine frequency behavior and related bandwidth parameters. This also allows for the processing of motor trajectories. Torque is indeed directly related to acceleration and, consequently, to velocity.

[0016] Optionally, the predetermined torque sequence includes a first torque oscillation sequence at a first frequency and a second torque oscillation sequence at a second frequency, where the first frequency is different from the second frequency. This configuration allows the behavior of the torque sensor at different frequencies to be determined, thereby determining frequency-related parameters.

[0017] Optionally, the method also includes user-triggered execution, measurement, comparison, and determination of the electric motor. This user-triggered execution gives the user the possibility to adjust the torque sensor transfer function parameters when needed, rather than relying on potentially inaccurate predetermined parameters.

[0018] Optionally, the method also includes periodically repeating the execution, measurement, comparison, and determination. This periodicity allows the variable speed drive to maintain satisfactory performance over time.

[0019] Optionally, this method is applied to each start-up of the transmission drive. This allows for systematic adjustment of the torque sensor transfer function parameters.

[0020] Optionally, the method also includes recording the evolution of one or more torque sensor transfer function parameters over time. Maintaining such records can help identify problems. In some cases, the method also includes providing torque sensor condition diagnostics based on deviations of one or more torque sensor transfer function parameters from predetermined ranges. Identifying such deviations may allow for the identification of undesirable behaviors or conditions.

[0021] Optionally, the method includes considering one or more torque sensor transfer function parameters when driving the electric motor. While determining these parameters allows for the evaluation of the characteristics of the torque sensor or the electric motor, considering these parameters when driving the electric motor allows for more accurate and satisfactory driving of the motor.

[0022] This disclosure also describes a computer-readable storage medium including instructions that, when executed by a processor, cause the processor to perform any of the methods described herein. Such a computer-readable storage medium enables the encoding of any of the methods described herein on a computing system.

[0023] This disclosure also describes a variable speed drive for an electric motor, including a processor and memory, the processor being configured to operate according to any of the methods described herein. Such a variable speed drive allows for the realization of the advantages of the methods. Attached Figure Description

[0024] Figure 1 An example method is shown.

[0025] Figure 2 Another example method is shown.

[0026] Figure 3 Another example method is shown.

[0027] Figure 4 Another example method is shown.

[0028] Figure 5 Another example method is shown.

[0029] Figure 6 Another example method is shown.

[0030] Figure 7 Another example method is shown.

[0031] Figure 8 An example variable speed drive is shown.

[0032] Figure 9 Another example of a variable speed drive is shown.

[0033] Figure 10A -D shows another example method. Detailed Implementation

[0034] This disclosure applies to variable speed drives for controlling electric motors. In this disclosure, a variable speed drive should be understood as a control unit for an electric motor, implemented electronically, virtually, or in software. In some examples, the variable speed drive includes processing and control units designed to implement control laws by considering, for example, an input speed setpoint, the voltage applied to the electric motor during normal motor operation, and control commands applied to an inverter stage to obtain these output voltages. The control laws can be vector or scalar type. The variable speed drive may include a rectifier stage at its input for converting AC voltage supplied by the power grid into DC voltage. The variable speed drive may also include a DC power bus connected to both the rectifier stage and the inverter stage. The DC power bus may include two power lines connected together by at least one bus capacitor configured to stabilize the bus voltage. The rectifier may be passive, such as a diode bridge, or active, based on controlled transistors. The inverter stage can be connected to the output of the DC power bus and used to cut off the bus to supply a variable voltage to the electric motor. The inverter stage includes, for example, multiple switching arms, each including a controlled power transistor of type IGBT, for applying a variable voltage to the electric motor. The inverter can be controlled using conventional techniques such as PWW (Pulse Width Modulation) or DTC (Direct Torque Control). The control law executed by the processing unit UC allows the determination of the voltage to be applied to the output phase connected to the motor to be controlled.

[0035] According to this disclosure, a transmission drive is connected to a torque sensor for sensing torque provided by an electric motor. In this disclosure, a torque sensor should be understood as a device that measures the torque generated by the shaft of the electric motor. In some examples, the torque sensor is a rotary torque sensor aligned with the shaft of the electric motor, located between the motor and its load. The torque sensor may rely on different technologies to measure torque. An advantage of the method according to this disclosure is that this method can be used regardless of the type of technology used by the torque sensor. According to this disclosure, the torque sensor is actually represented by a torque sensor transfer function, which virtually encodes the behavior of the torque sensor. The transfer function should be understood as a function with inputs and outputs, the inputs including, for example, a torque scalar value corresponding to the output of the torque sensor, and the output of the transfer function including, for example, a torque scalar value corresponding to the torque value to be considered by the transmission drive, whereby the torque value output by the transfer function will be more accurate than the torque scalar value corresponding to the output of the torque sensor. In some examples, the transfer function models the torque output based on the torque input. In some examples, the transfer function is represented as a Laplace transform. The transmission drive and the torque sensor are connected. The connection between the torque sensor and the transmission drive allows the transmission drive to receive data related to torque measurements taken by the torque sensor. This data can be analog or digital. It can be transmitted wirelessly or via cable.

[0036] To ensure stable and effective control, the variable speed drive preferably incorporates multiple sensor measurements, particularly torque sensor measurements, which measure the torque generated by the electric motor. Inaccurate torque measurements during control operation can lead to performance degradation. Specifically, torque sensors may overestimate or underestimate the torque generated by the motor, especially in the case of dynamic torque, which is, for example, a torque whose value varies by at least 20% over a time range of less than 0.25 seconds, less than 10 ms, less than 5 ms, or less than 2 ms. To avoid these problems, a method according to this disclosure is provided.

[0037] Figure 1An example method 100 according to this disclosure is illustrated. As shown in box 101, method 100 includes executing a predetermined torque sequence by an electric motor. The predetermined torque sequence should be understood as a specific command applied to the electric motor by a transmission drive within a specific time period. The specific time period may be less than 60 seconds and greater than 0.5 seconds. The specific time period may be less than 40 seconds and greater than 5 seconds. The specific time period may be less than 40 seconds and greater than 20 seconds. In some examples, the specific time period is less than 5 seconds and greater than 1 second. The specific command may directly produce the predetermined torque sequence, for example, if the command is directly applied as a torque command applied to the electric motor by the transmission drive. The specific command may also indirectly result in the predetermined torque sequence, for example, if the command is applied using a characteristic indirectly related to torque, such as tension, strength, or other such characteristics. The torque sequence is predetermined because the torque sequence has a specific profile designed to achieve the method according to this disclosure, which will be described in more detail herein.

[0038] As shown in box 102, method 100 includes measuring a measured torque sequence corresponding to a predetermined torque sequence using a torque sensor. This measurement can be performed using torque sensing technology of the torque sensor. This measured torque sequence may differ from the predetermined torque sequence for a variety of reasons. These reasons include the possibility that the effective command transmitted to the electric motor may differ from the predetermined torque sequence, for example, due to the characteristics of components in the transmission drive. These reasons may also include the possibility that the electric motor does not accurately reproduce the torque according to the transmitted effective command. These reasons also include the possibility that the torque sensor itself may not transmit the measured precise torque as a measurement. All these sources of inaccuracy may be included in the measured torque sequence to be processed according to this disclosure. Therefore, the method according to this disclosure will take into account such possible combinations of deviations from the theoretically predetermined torque sequence.

[0039] As shown in box 103, method 100 includes comparing a predetermined torque sequence and a measured torque sequence. This comparison can be performed using a controller of a transmission drive. Alternatively, this comparison can be performed using a processing unit other than the controller of the transmission drive, such as a remote processing unit. This comparison allows for the identification of deviations between the predetermined torque sequence and the measured torque sequence. This comparison may include generating data representing the differences between the predetermined torque sequence and the measured torque sequence.

[0040] As shown in box 104, method 100 includes determining one or more torque sensor transfer function parameters as a result of a comparison. The torque sensor transfer function parameters should be understood as scalar, vector, or matrix parameters that, when adjusted, change the output of the corresponding torque sensor transfer function when given a specific input. For torque measurement purposes, these parameters can be adjusted so that the torque sensor transfer function represents the behavior of a system including a transmission drive, a torque sensor, and an electric motor. This adjustment can be achieved by considering multiple candidate torque sensor transfer functions, each associated with corresponding candidate parameters, and by selecting a candidate torque sensor transfer function that provides an output closer to the measured torque sequence when the input is a predetermined torque sequence. The parameters can also be determined based on the comparison characteristics between the measured torque and the predetermined torque. This determination of one or more torque parameters allows for consideration of dynamic torque, rather than relying on static torque to drive the electric motor.

[0041] In some examples, one or more torque sensor transfer function parameters, such as those defined in box 104, include one or more of a delay parameter, a gain parameter, or a bandwidth parameter. A delay parameter should be understood as a parameter relating to the time delay between a change in torque value included in a predetermined torque sequence and the perception of such a change in the measured torque sequence. In some examples, this delay may be less than 1 second. In some examples, this delay may be less than 0.5 seconds. In some examples, this delay may be less than 0.3 seconds. A gain parameter should be understood as a coefficient or factor that adjusts the measured torque value to the actual torque value at a given time. In some examples, if the predetermined torque sequence includes a static torque portion, this static torque portion may allow the gain parameter to be determined by adjusting the torque sensor transfer function with the gain parameter to reflect that the measured torque should correspond to the predetermined torque when in a static state. A bandwidth parameter may reflect the ability of the entire system to perform within a specific frequency bandwidth of torque oscillations. In some examples, while the entire system including the transmission drive, torque sensor, and electric motor may behave consistent with a portion of the predetermined torque sequence where torque varies at a relatively low frequency, the same entire system may not behave consistent with a portion of the predetermined torque sequence where torque varies at a relatively high frequency. In some examples, the entire system exhibits behavior that can be reflected by a low-pass filter. In some examples, the bandwidth parameter corresponds to the cutoff frequency of the low-pass filter that reflects the behavior of the variable speed drive and the electric motor driven by the variable speed drive.

[0042] In some examples, the predetermined torque sequence executed by the electric motor according to box 101 includes one or more torque steps. A torque step should be understood as part of the predetermined torque sequence, comprising a steep change in torque value from a first specific torque value to a second specific torque value, the first torque value being different from the second torque value. The steep change in torque value can be a change in value from zero torque value to a non-zero torque value. In the predetermined torque sequence, the change in torque value can be instantaneous. In the predetermined torque sequence, the change in torque value can occur within a finite time period, for example, less than 0.1 seconds. In the predetermined torque sequence, the change in torque value can occur within a finite time period, for example, less than 0.05 seconds. In the predetermined torque sequence, the change in torque value can occur within a finite time period, for example, less than 0.02 seconds. In the predetermined torque sequence, the change in torque value can occur within a finite time period, for example, less than 0.01 seconds. In some examples, the change in torque value can be greater than 10% of the second torque value. Such torque steps may be particularly suitable for determining a delay parameter related to the time it takes for the measured torque to catch up with the torque change. Once the value changes, the torque can be held for a minimum time period to produce a step, allowing the entire system to stabilize at that held torque value. In some examples, this torque value corresponding to the step is held for at least 0.5 seconds. In some examples, this torque value corresponding to the step is held for at least 1 second. In some examples, the torque sequence includes multiple torque steps. Multiple torque steps can include torque variations alternating between a first torque value and a second torque value, which are held during a static torque period, for example, at least 0.5 seconds. In some examples, multiple torque steps include two or more torque variations between different torque values, thereby selecting different torque values ​​from at least three different torque values. In some examples, multiple torque steps include a first portion where the predetermined torque value is zero, lasting approximately 1 second, followed immediately by a second portion where the predetermined torque value has a second value other than zero, held for approximately 1 second, followed immediately by a third portion where the predetermined torque value has a third value opposite to the second value, held for approximately 1 second, followed immediately by a fourth portion where the predetermined torque value has a fourth value corresponding to the second value, held for approximately 1 second. Using multiple steps can improve the accuracy of determining parameters such as delay parameters, for example, by allowing averaging of parameter values. Sequences including one or more steps may also be particularly well-suited for determining gain parameters, since the measured torque should correspond to a predetermined torque value once it reaches that value after a change. In some examples, torque steps involve acquiring and holding a torque value that falls between the nominal torque of the electric motor in a first rotational direction and the nominal torque of the electric motor in the opposite rotational direction.

[0043] In some examples, the predetermined torque sequence executed by the electric motor according to block 101 includes chirped torque oscillations. Chirped torque oscillations should be understood to include a pseudo-sinusoidal signal whose frequency varies with time. In some examples, the frequency of the chirped torque oscillations increases with time. In some examples, the chirped signal has a frequency greater than 0.2 Hz and less than 20 Hz. In some examples, the chirped signal starts at a frequency of approximately 1 Hz and gradually reaches a frequency of approximately 10 Hz. In some examples, the chirped signal has a constant amplitude. In some examples, the chirped signal has an amplitude that varies with time. In some examples, the chirped signal has a higher amplitude at lower frequencies and a lower amplitude at higher frequencies. In some examples, the chirped signal has a lower amplitude at lower frequencies and a higher amplitude at higher frequencies, for example, to account for the mechanical inertia of the motor. In some examples, the amplitude of the chirp signal may include between 75% of the nominal torque of the electric motor in the first rotational direction and 75% of the nominal torque of the electric motor in the opposite rotational direction. In some examples, the amplitude of the chirp signal may include between 50% of the nominal torque of the electric motor in the first rotational direction and 50% of the nominal torque of the electric motor in the opposite rotational direction. In some examples, the amplitude of the chirp signal may include between the nominal torque of the electric motor in the first rotational direction and the nominal torque of the electric motor in the opposite rotational direction. The chirp oscillation according to this disclosure may be very suitable for determining bandwidth parameters associated with the cutoff frequency. For example, due to mechanical inertia, the behavior of an electric motor does indeed more closely follow a predetermined torque sequence at a lower frequency compared to a predetermined torque sequence at a higher frequency. The chirp signal thus allows for the determination of a torque frequency or torque frequency range in which the electric motor exhibits difficulty in following the predetermined torque sequence.

[0044] In some examples, the predetermined torque sequence executed by the electric motor according to block 101 includes one or more torque steps followed by chirped torque oscillations. A reverse sequence is also possible. This configuration allows, for example, the use of one or more torque steps to determine gain and delay parameters, and the use of a chirped signal to determine bandwidth parameters. In some examples, such torque steps include alternating torque steps between the nominal torque of the engine in a first rotational direction and the nominal torque of the engine in the opposite rotational direction, resulting in a torque change corresponding to twice the amplitude of the nominal torque. This significant change allows the delay parameters to be determined with particularly significant accuracy. In some examples, the chirped signal has a constant amplitude corresponding to approximately 25% of the nominal torque of the electric motor. Using a relatively low chirped signal amplitude value compared to the torque value used for the steps allows for a reduction in the effects of mechanical inertia as the electric motor follows the chirped signal. In some examples, one or more torque steps include a first step of approximately one second when the torque is zero, a second step of approximately one second at the nominal torque immediately following the first step, a third step of approximately one second at the opposite nominal torque immediately following the second step, and a fourth step of approximately one second at the nominal torque immediately following the third step. A chirped signal with an amplitude of approximately 25% of the nominal torque is applied directly after the fourth step. The chirped signal starts at approximately 1 Hz and continuously advances to a frequency of approximately 10 Hz over approximately 25 seconds, with the entire predetermined torque sequence lasting approximately 30 seconds. In practice, in some examples, one or more torque steps are at the first torque amplitude, and the chirped torque oscillation is at the second torque amplitude, which is lower than the first torque amplitude. In some examples, the second torque amplitude is less than one-quarter of the first torque amplitude. In some examples, the second torque amplitude is less than half of the first torque amplitude. In some examples, the second torque amplitude is less than three-quarters of the first torque amplitude. In some examples, the chirped signal has an amplitude of approximately 25% of the nominal torque. The chirped signal begins at approximately 1 Hz and progresses to approximately 10 Hz by following different frequency levels. The frequency remains stable at a given level, and the progression occurs within approximately 25 seconds. The entire predetermined torque sequence lasts for approximately 30 seconds, with each level lasting, for example, approximately 2.5 seconds, followed by another level with a frequency approximately 1 Hz higher than the previous level. In practice, in some examples, the predetermined torque sequence includes a first torque oscillation sequence at a first frequency and a second torque oscillation sequence at a second frequency, the first frequency being different from the second frequency.

[0045] Figure 2 An example method 200 according to this disclosure is shown. Method 200 includes... Figure 1Boxes 101-104 described herein are consistent with boxes 101-104. Method 200 also includes box 205: user-triggered execution, measurement, comparison, and determination of the electric motor. This triggering can occur in response to a user action. An example user action is the actuation of a mechanical button. An example user action is the actuation of a graphical button on a graphical transmission drive interface. The user can trigger this action in response to observing a problem with the electric motor or transmission drive. This user triggering may prevent the method according to this description from being performed at a time when it is inconvenient for the user.

[0046] Figure 3 An example method 300 according to this disclosure is shown. Method 300 includes... Figure 1 Boxes 101-104 described herein are consistent with boxes 101-104. Method 300 also includes periodically repeating the execution, measurement, comparison, and determination. This period can be set by the user, for example. Example periods could be once a day, once a month, or once a year. This period can be set after the electric motor has been used for a certain period of time. This period can be set according to a specific schedule suitable for a particular motor type or suitable for a torque sensor, for example by shortening the period as the electric motor ages. This period can be set remotely, for example, by the electric motor or transmission drive manufacturer or the torque sensor manufacturer.

[0047] Figure 4 An example method 400 according to this disclosure is shown. Method 400 includes... Figure 1 Boxes 101-104 described herein are consistent with boxes 101-104. Method 400 also includes box 406: starting the electric motor, which is followed by the application of execution, measurement, comparison, and determination at each start of the transmission drive. According to this disclosure, this can allow ensuring that the electric motor is driven with updated parameters.

[0048] Figure 5 An example method 500 according to this disclosure is shown. Method 500 includes... Figure 1 Boxes 101-104 described herein are consistent with boxes 101-104. Method 500 also includes box 507: recording the evolution of one or more torque sensor transfer function parameters over time. Such evolution records may, for example, be stored in the memory of the transmission drive according to this disclosure. Such evolution records may also be, or alternatively, stored remotely. Such evolution records may be stored on a centralized data custodian that stores evolution records corresponding to multiple transmission drives, thereby allowing comparison of the evolution of such transmission drives and corresponding electric motors. Such a centralized data custodian may be maintained by the manufacturer of the electric motor or transmission drive to monitor multiple transmission drives and electric motors, thereby allowing preventative measures to be implemented in the event of a specific evolution of a particular type of transmission drive, electric motor, or torque sensor.

[0049] Figure 6 An example method 600 according to this disclosure is shown. Method 600 includes... Figure 1 Boxes 101-104 described herein are consistent with boxes 101-104. Method 600 includes boxes 101-104. Figure 5 The method 600 is consistent with box 507 described in the previous section. The method also includes box 608: providing torque sensor condition diagnostics based on deviations of one or more torque sensor transfer function parameters from a predetermined range. Providing such diagnostics can allow for the prevention or resolution of problems that would otherwise negatively impact the operation of the electric motor and / or transmission drive. By applying the method according to this disclosure, the expected lifespan of the electric motor, transmission drive, or torque sensor can indeed be extended.

[0050] Figure 7 An example method 700 according to this disclosure is shown. Method 700 includes... Figure 1 The blocks 101-104 described herein are consistent with blocks 101-104. Method 700 also includes driving the electric motor in block 709 by taking into account one or more torque sensor transfer function parameters. This not only allows the method according to this disclosure to be used for diagnostic purposes, but also allows for improving the operating accuracy of the corresponding electric motor, thereby allowing the control feedback loop that takes into account the measured torque to be implemented with greater precision by implementing a torque sensor transfer function that includes one or more defined torque sensor transfer function parameters.

[0051] Figure 8 An example variable speed drive 800 is shown, including a processor 801 and a memory 802. The processor 801 is configured to operate according to any of the methods described herein. The processor 801 may include electronic circuitry for computations managed by an operating system.

[0052] Figure 8 Also shown is a non-transitory machine-readable or computer-readable storage medium, such as a memory or storage cell 802, wherein the non-transitory machine-readable storage medium is encoded with instructions 803 executable by a processor, such as processor 801, the machine-readable storage medium including instructions 803 to operate processor 801 to execute according to any example methods described herein.

[0053] The computer-readable storage according to this disclosure can be any electronic, magnetic, optical, or other physical storage device storing executable instructions. Computer-readable storage can be, for example, random access memory (RAM), electrically erasable programmable read-only memory (EEPROM), storage drives, and optical discs. As described herein, computer-readable storage can be encoded with executable instructions according to the methods described herein.

[0054] Storage or memory can include any electronic, magnetic, optical or other physical storage device that stores executable instructions as described herein.

[0055] Figure 9 An example transmission drive 900 is shown, including a processor 901 and a memory 902. The processor 901 is configured to operate according to any of the methods described herein. The processor 901 may include electronic circuitry for computations managed by an operating system. The transmission drive 900 also includes a network module 904. The network module 904 allows data related to torque sensor transfer function parameters to a centralized data register 910 according to this disclosure. According to this disclosure, the centralized register 910 may be sequentially connected to a plurality of transmission drives 911-914. Such a centralized register can collect torque sensor transfer function parameters according to this disclosure in its memory. The centralized register uses its processing unit or processor to process such collected transfer function parameters in order to monitor multiple transmission drives connected to or networked to the centralized register.

[0056] Figure 10A A specific example method 1000 according to this disclosure is illustrated. In a first step, the method includes starting a timer for generating a torque step as part of a predetermined torque sequence to be executed by an electric motor. A measured torque is compared to a measured torque threshold, which may, for example, correspond to 5% of the amplitude of the torque step in the predetermined torque sequence, for example... Figure 10B As shown, the torque sequence is represented by dashed lines, and the measured torque is represented by solid lines. Detecting that the measured torque exceeds a torque threshold corresponds to detecting that the electric motor has started responding to a predetermined torque sequence. Figure 10B As shown, the delay τ between the moment the torque step is applied and the moment the measured torque reaches the threshold is... r This corresponds to the delay parameter. In this example, the delay parameter is determined when the measured torque reaches a 5% threshold, but other thresholds may be considered. In some examples, the delay is determined when the measured torque reaches X% of the torque value applied by the transmission drive as part of a torque sequence. In some examples, X is a number between 1 and 99. In some examples, X is a number between 2 and 50. In some examples, X is a number between 3 and 30. In some examples, X is a number between 3.5 and 20. In some examples, X is a number between 4 and 10. Figure 10B In the example, τ r The value is approximately 0.02 seconds. For example... Figure 10A As shown, after determining the delay parameters, the next step is to search for the variable speed drive start-up cutoff frequency; in other words, this is applied to, for example... Figure 10C Or the electric motor portion of the predetermined torque sequence of torque oscillation shown in 10D, in Figure 10C In this case, the oscillation begins after 5 seconds, with the first 5 seconds used to determine the delay parameter. For example... Figure 10A and 10C As shown, the generated pulsation rate (e.g.) Figure 10C (Radians per second) or frequency gradually increases. Figure 10C In the diagram, the dashed line represents the measured torque, and the solid line represents the predetermined sequence applied by the transmission drive to the electric motor. For example... Figure 10C As shown, the measured torque amplitude lags as the frequency increases. This allows the cutoff frequency parameter to be determined according to this disclosure. Figure 10A In the examples shown, the cutoff frequency parameter corresponds to the frequency at which the amplitude of the measured signal represents half or 50% of the amplitude of the corresponding predetermined sequence signal. In other cases, different percentages or values ​​may be used to determine the cutoff frequency. In some examples, the cutoff frequency parameter is determined to be the frequency at which the measured torque amplitude represents Y% of the amplitude of the corresponding predetermined sequence torque. In some examples, Y is a number between 90 and 10. In some examples, Y is a number between 80 and 20. In some examples, Y is a number between 70 and 30. In some examples, Y is a number between 60 and 40. Figure 10C In this case, the predetermined torque sequence includes a gradually increasing torque oscillation frequency, in this example, increasing in steps of 5 radians per second, with each step lasting approximately 5 seconds. Other step values ​​may be considered in other examples. Figure 10D Specifically Figure 10C It is part of a predetermined sequence, which includes torque oscillations that result in a determined cutoff frequency. Figure 10D In this case, the measured torque is represented by a solid line, and the predetermined sequence is represented by a dashed line. The solid line segment represents the torque amplitude value measured at a given frequency. Figure 10D As shown, the measured torque amplitude gradually decreases as the frequency increases, compared to the amplitude according to the predetermined sequence.

[0057] Example torque sensor transfer functions include:

[0058]

[0059] Where H is the transfer function in the Laplace space, and s is in the s space. -1 Therefore, τ r τ2 is determined as the delay parameter, and τ2 is determined as the bandwidth parameter or cutoff frequency parameter.

Claims

1. A method for controlling a variable speed drive for an electric motor, the variable speed drive being connected to a torque sensor for sensing torque provided by the electric motor, the method comprising: - A predetermined torque sequence is executed by an electric motor; - A measured torque sequence corresponding to a predetermined torque sequence is measured by a torque sensor; - Compare the predetermined torque sequence with the measured torque sequence; as well as As a result of the comparison, one or more torque sensor transfer function parameters are determined for the torque sensor transfer function, which is configured to output a measured value of the torque provided by the electric motor for use by the transmission drive based on the measured torque from the torque sensor and the one or more torque sensor transfer function parameters.

2. The method according to claim 1, wherein, The transfer function parameters of the one or more torque sensors include one or more of the following: delay parameter, gain parameter, or bandwidth parameter.

3. The method according to claim 2, wherein, The predetermined torque sequence includes one or more torque steps.

4. The method according to claim 3, wherein, The predetermined torque sequence includes chirped torque oscillations.

5. The method according to claim 4, wherein, The predetermined torque sequence includes one or more torque steps, followed by chirped torque oscillations.

6. The method according to claim 5, wherein, The one or more torque steps are at a first torque amplitude, and the chirped torque oscillation is at a second torque amplitude, which is lower than the first torque amplitude.

7. The method according to claim 1, wherein, The predetermined torque sequence includes a first torque oscillation sequence at a first frequency and a second torque oscillation sequence at a second frequency, wherein the first frequency is different from the second frequency.

8. The method of claim 1, further comprising the execution, measurement, comparison, and determination triggered by a user of the electric motor.

9. The method of claim 1, further comprising periodically repeating the execution, measurement, comparison, and determination.

10. The method of claim 1, wherein the method is applied to each start-up of the variable speed drive.

11. The method of claim 1, further comprising recording the evolution of one or more torque sensor transfer function parameters over time.

12. The method of claim 11, further comprising providing torque sensor condition diagnosis based on deviations of the transfer function parameters of the one or more torque sensors from a predetermined range.

13. The method of claim 1, wherein the method includes driving the electric motor by taking into account the transfer function parameters of the one or more torque sensors.

14. A computer-readable storage medium comprising instructions that, when executed by a processor, cause the processor to perform the method of any one of the preceding claims.

15. A variable speed drive for an electric motor, comprising a processor and a memory, the processor being configured to operate according to any one of the preceding method claims.

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