Motor using single sensor, application and high-precision rotating speed calculation method

Abstract

The invention discloses a motor using a single sensor, an application and a high-precision rotating speed calculation method, the motor is provided with the single sensor, the rotating speed and the rotating direction of the motor are detected through the single sensor, and the sensor is a Hall sensor or an encoder; the motor is applied to a driving mechanism with a self-locking structure. The high-precision rotating speed calculation method comprises the following steps: step 1, obtaining the rotating direction of the motor according to the input voltage direction or the current direction of the motor, step 2, measuring to obtain the pulse number Np of a sensor, step 3, obtaining the estimated speed of the motor through the input voltage, the duty ratio, the current and the total resistance, and step 4, calculating the rotating speed of the motor according to the estimated speed. 4, obtaining an estimated pulse number according to the estimated speed, and 5, calculating the rotating speed of the motor according to the measured pulse number Np and the estimated pulse number. The method has the advantages that the motor cost can be reduced, the pin consumption of the single-chip microcomputer is reduced, and the measurement precision is high.

Description

Technical Field

[0001] The present invention belongs to the field of motors, and in particular relates to a motor using a single sensor, an application and a high-precision rotation speed calculation method. Background Art

[0002] In conventional applications, at least two sensors (Hall sensors or encoders) are required to detect the direction of motor rotation, because the direction of rotation can only be achieved by comparing the phase shift of the output levels of the two sensors.

[0003] In addition, the output of the sensor can only be 0 or 1. Conventional speed calculation methods such as Figure 3 The figure shows the pulse calculation method. Under the conventional speed calculation method, when the motor speed is low and the processing time is low (the speed loop sampling frequency is high), it may cause obvious quantization errors.

[0004] The cause of quantization error is, for example, if the motor speed is only 300RPM (5Hz), if a Hall falling edge detection is used, only 5 Hall signals can be collected per second. If the speed loop sampling time is 0.1s, 10 samples will be collected in one second, which will cause the speed to display 0 for half of the time and 600RPM for half of the time. Because there are only five signals in 1 second. Therefore, this phenomenon is more obvious at low speed or high sampling frequency.

[0005] If no or only one Hall effect sensor is used, the quantization error will increase significantly, which will further affect the speed estimation accuracy.

[0006] Since existing motors use two sensors to find the direction of rotation and improve the speed detection accuracy, this leads to higher motor costs and a corresponding increase in the failure rate. Summary of the invention

[0007] The purpose of the present invention is to provide a motor using a single sensor, an application and a high-precision speed calculation method. The present invention has the advantages of reducing the cost of the motor, reducing the number of microcontroller pins and having high measurement accuracy.

[0008] The technical solution of the present invention is to use a single-sensor motor, in which a single sensor is provided, and the rotation speed and rotation direction of the motor are detected by the single sensor, and the sensor is a Hall sensor or an encoder.

[0009] In the aforementioned motor, a driver is connected to the motor.

[0010] The aforementioned motor is used in a driving mechanism with a self-locking structure.

[0011] In the aforementioned application, the driving mechanism with a self-locking structure is a worm gear type gearbox, the gearbox is used on the lifting table, and the motor drives the lifting table through the gearbox to achieve the lifting action.

[0012] The above-mentioned high-precision speed calculation method of the motor includes the following steps:

[0013] Step 1: Get the rotation direction of the motor according to the input voltage direction or current direction of the motor.

[0014] Step 2: Measure the pulse number Np of the sensor.

[0015] Step 3: Input voltage V in , duty cycle D, current I DC And the total resistance R T , get the estimated speed ω of the motor est ,

[0016] Step 4: According to the estimated speed ω est Get the estimated pulse number Np (est，i) ,

[0017] Step 5: Based on the measured pulse number Np and the estimated pulse number Np (est，i) , calculate the motor speed ω actual .

[0018] In the above-mentioned method for calculating the high-precision speed of the motor, in step 3, the estimated speed ω is calculated using formula (eq.3) est ,

[0019]

[0020] V in is the input voltage of the motor, D is the duty cycle, I DC is the current, R T is the total resistance, that is, the resistance of the motor and the circuit, and Ke is the back EMF constant.

[0021] In the above-mentioned high-precision speed calculation method of the motor, in step 4, the estimated pulse number Np is calculated using formula (eq.4): (est，i) ,

[0022] Formula (eq.4):

[0023] Np (est，i) is the estimated number of pulses in the current cycle. When the falling edge of the Hall is detected, Np (est，i) =0, Np (est，i-1) is the estimated number of pulses in the previous cycle, T s(calc) It is the cycle time for detecting the motor speed.

[0024] In the method for calculating the high-precision rotation speed of the motor, in step 5, the rotation speed of the motor is calculated using formula (eq.5),

[0025] Formula (eq.5):

[0026] T s(speed) is the speed sampling time, and P is the number of pole pairs of the Hall magnetic ring.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] 1) Save the number of sensors, thereby reducing the cost of the motor, and improve the measurement accuracy of the motor speed under a specific calculation method.

[0029] 2) Since the number of sensors is reduced from two to one, the number of pins on a single chip can be reduced. In some cases, such as multi-motor control systems, one extra pin may require an additional microcontroller, which helps reduce the cost of the motor control system.

[0030] 3) Under a specific calculation method, the estimated speed can be continued to be used when the sensor signal is lost, that is, it can continue to be used when the sensor fails.

[0031] 4) If the speed is calculated by pure motor sensorless method (i.e., the motor speed is derived by detecting the back electromotive force of the motor), it is easy to make mistakes due to the current measurement noise, especially when the motor rotates at a low speed. In addition, the change of motor parameters due to temperature and aging will greatly reduce the accuracy. The present invention uses a Hall effect sensor as a supporting device to overcome the shortcomings of pure motor sensorless speed calculation. The sensor can be used as an anchor point for speed measurement, so that the measurement accuracy is high.

[0032] In summary, the present invention has the advantages of reducing the cost of the motor, reducing the number of microcontroller pins and having high measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the present invention.

[0034] Figure 2 This is the schematic diagram of the driver.

[0035] Figure 3 This is the schematic diagram of the conventional speed calculation method. DETAILED DESCRIPTION

[0036] The present invention is further described below in conjunction with the accompanying drawings and embodiments, but they are not intended to limit the present invention.

[0037] Embodiment 1. A single-sensor motor is used, wherein a single sensor is provided in the motor, and the speed and rotation direction of the motor are detected by the single sensor, wherein the sensor is a Hall sensor or an encoder. The motor is a brushed DC motor, and a driver is connected to the motor and connected to the control system of the motor.

[0038] Embodiment 2: The motor of embodiment 1 is applied to a driving mechanism with a self-locking structure, wherein the driving mechanism with a self-locking structure is a worm gear type gearbox, the gearbox is used on a lifting table, and the motor drives the lifting table through the gearbox to achieve lifting action.

[0039] Embodiment 3. The high-precision speed calculation method of the motor of Embodiment 1 comprises the following steps:

[0040] Step 1: Get the rotation direction of the motor according to the direction of the motor's input voltage or current. The positive and negative input voltages of the motor can be found through the H-bridge transistor switch.

[0041] Principle of step 1: Figure 2 As shown in the figure, when driving the motor, the positive and negative torque (T m ) can be selected by the direction of the current flowing into the motor, selecting one pair of Q1 / Q4 or Q2 / Q3 to energize.

[0042] Formula (eq.1): T m =k t =I DC .

[0043] kt is the motor torque constant, I DC is the motor current.

[0044] The rotational acceleration (α) of the motor depends on the external load (T L ), motor torque (T m ) and moment of inertia (J):

[0045] Formula (eq.2):

[0046] For a power system with self-locking capability, when the external load is less than the self-locking power, the load will not cause the motor shaft to rotate. From formula (eq.2), we can see that if T L Greater than T m The transmission system will enter a self-locking state. m Greater than T L Only then can it turn.

[0047] Based on this factor, the direction of rotation of the motor can be estimated by the input voltage (or current) of the motor, because the direction of torque is consistent with the direction of rotation. Therefore, a single Hall sensor can achieve speed prediction.

[0048] In Example 3, a brushed DC motor is used as an example, but other motors are also applicable because the self-locking structure will make the torque direction and rotation direction of any motor consistent.

[0049] In step 1, the direction of the motor's rotation can be estimated by checking the input voltage or current direction. In this case, there is no need to use the phase shift of the dual Hall signals to estimate the motor's rotation direction as is typical, a single Hall is sufficient.

[0050] Step 2: Measure the pulse number Np of the sensor (it must be an integer).

[0051] Step 3: Use formula (eq.3) to calculate the estimated speed ω of the motor rotation est .

[0052] Formula (eq.3):

[0053] In formula (eq.3), V in is the input voltage of the motor, D is the duty cycle, I DC is the current, R T is the total resistance, that is, the resistance of the motor and the circuit, and Ke is the back EMF constant.

[0054] Step 4: Use formula (eq.4) to calculate the estimated pulse number Np (est，i) (decimal),

[0055] Formula (eq.4):

[0056] In formula (eq.4), Np (est，i) Is the estimated number of pulses in the current cycle. If the falling edge of the Hall is detected, Np (est，i) = 0. Np (est，i-1) is the estimated number of pulses in the previous cycle, T s(calc) It is the cycle time for the controller in the control system to detect the motor speed.

[0057] Step 5: Use formula (eq.5) to calculate the motor speed ω actual .

[0058] Formula (eq.5):

[0059] In formula (eq.5), T s(speed) is the speed sampling time, and P is the number of pole pairs of the Hall magnetic ring.

[0060] In Example 3, assuming the motor is a 2-pole DC brushed motor with a 2-pole magnetic ring, rotating at 3000 RPM, each Hall effect cycle will be 20ms. If the sampling time or controller calculation cycle is 1ms, then after detecting a 0 output, the control algorithm needs to add 0.05 to the Hall effect sensor output. This will repeat until the next Hall 0 signal is detected.

Claims

1. A motor using a single sensor, characterized in that: A single sensor is provided in the motor, and the rotation speed and rotation direction of the motor are detected by the single sensor. The sensor is a Hall sensor or an encoder.

2. The motor according to claim 1, characterized in that: The motor is connected with a driver.

3. Application of the motor according to claim 1 or 2 in a drive mechanism with a self-locking structure.

4. The method according to claim 3, characterized in that: The driving mechanism with a self-locking structure is a worm gear type gearbox, which is used on the lifting table. The motor drives the lifting table through the gearbox to achieve lifting action.

5. The high-precision speed calculation method for a motor according to claim 1 or 2, characterized in that: The following steps are included: Step 1: Get the rotation direction of the motor according to the input voltage direction or current direction of the motor. Step 2: Measure the pulse number Np of the sensor. Step 3: Input voltage V in , duty cycle D, current I DC And the total resistance R T , get the estimated speed ω of the motor est , Step 4: According to the estimated speed ω est Get the estimated pulse number Np (est，i) , Step 5: Based on the measured pulse number Np and the estimated pulse number Np (est，i) , calculate the motor speed ω actual .

6. The high-precision speed calculation method for a motor according to claim 4, characterized in that: In step 3, the estimated speed ω is calculated using formula (eq.3) est , Formula (eq.3): V in is the input voltage of the motor, D is the duty cycle, I DC is the current, R T is the total resistance, that is, the resistance of the motor and the circuit, and Ke is the back EMF constant.

7. The high-precision speed calculation method for a motor according to claim 5, characterized in that: In the step 4, the estimated pulse number Np(est,i) is calculated using formula (eq.4), Formula (eq.4): Np (est，i) is the estimated number of pulses in the current cycle. When the falling edge of the Hall is detected, Np (est，i) =0, Np (est，i-1) is the estimated number of pulses in the previous cycle, T s(calc) It is the cycle time for detecting the motor speed.

8. The method for calculating the high-precision rotation speed of a motor according to claim 6, characterized in that: In step 5, the motor speed is calculated using formula (eq.5): Formula (eq.5): T s(speed) is the speed sampling time, and P is the number of pole pairs of the Hall magnetic ring.

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