High-rigidity dual-motor complementary power shaft device

Abstract

The utility model discloses a high-rigidity dual-motor complementary power shaft device and belongs to the technical field of mechano-electronics. The fourth shaft complementary shaft power device is divided into a single index plate; the fourth shaft is superposed with the fifth shaft to form a complementary shaft power device; the mounting positions of the two motors require that stepping angle nodes are staggered to form a mutual insertion state; one stepping motor serves as a conventional path to cruise; the other motor is used for path offset compensation; deviation is detected by a sensor, and then real-time driving torque is generated by the full-time motor, so that path deviation is corrected in time; the system can be expanded to three-motor, four-motor and five-motor conditions, and the high-rigidity response capability and the machining precision of the system are improved.

Description

Technical Field

[0001] The present invention belongs to the field of mechatronics technology. Specifically speaking, it is a parallel special-purpose motor, which is a complementary drive device for improving the driving stiffness and accuracy of a stepping motor. Background Art

[0002] The original model of the stepping motor dates back to 1830. It is a motor that converts an electrical pulse signal into a corresponding angular displacement. For each input pulse signal, the rotor rotates by an angle. Its output angular displacement or linear displacement is proportional to the number of input pulses, and the rotational speed is proportional to the pulse frequency. It is an electromagnet that can rotate freely and generates electromagnetic torque by relying on the change of air-gap permeance. The biggest difference between the stepping motor and other motors for control purposes is that it can perform open-loop position control. By inputting a pulse signal, a specified position increment can be obtained. Compared with the traditional DC control system, the cost of such a so-called incremental position control system is significantly reduced, and almost no system adjustment is required. The angular displacement of the stepping motor is strictly proportional to the number of input pulses and is synchronized with the pulses in terms of time. Therefore, as long as the number, frequency of the pulses and the phase sequence of the motor windings are controlled, the required rotation angle, speed and direction can be obtained.

[0003] The rotational speed of the stepping motor depends on the pulse frequency, the number of rotor teeth and the number of beats. Its angular velocity is proportional to the pulse frequency and is synchronized with the pulses in terms of time. Therefore, when the number of rotor teeth and the number of operating beats are fixed, as long as the pulse frequency is controlled, the required speed can be obtained. The starting frequency characteristic of the stepping motor makes it impossible to directly reach the operating frequency when starting, but there must be a starting process, that is, gradually accelerating from a low rotational speed to the operating rotational speed. When stopping, the operating frequency cannot immediately drop to zero, but there must be a process of gradually decelerating from a high speed to zero.

[0004] The output torque of a stepper motor decreases as the pulse frequency increases. The higher the starting frequency, the smaller the starting torque, the poorer the ability to drive the load, and there will be loss of steps during startup and overshoot during stop. To enable the stepper motor to quickly reach the required speed without losing steps or overshooting, the key lies in ensuring that during the acceleration process, the torque required by the acceleration can fully utilize the torque provided by the stepper motor at each operating frequency without exceeding this torque. Therefore, the operation of a stepper motor generally goes through three stages: acceleration, constant speed, and deceleration, requiring the acceleration and deceleration process times to be as short as possible and the constant speed time to be as long as possible. Especially in applications that require fast response, the running time from the starting point to the end point is required to be the shortest, which necessitates the shortest acceleration and deceleration processes and the highest speed during constant speed. Scientists and technicians at home and abroad have conducted extensive research on the speed control technology of stepper motors, established various acceleration and deceleration control mathematical models, such as the exponential model, linear model, etc., and designed and developed various control circuits based on this, improving the motion characteristics of stepper motors and expanding the application range of stepper motors. Exponential acceleration and deceleration takes into account the inherent torque-frequency characteristics of stepper motors, which can not only ensure that the stepper motor does not lose steps during motion but also fully utilize the inherent characteristics of the motor, shortening the acceleration and deceleration times. However, due to changes in the motor load, it is difficult to implement. Linear acceleration and deceleration only consider the relationship that the angular velocity of the motor is proportional to the pulse within the load capacity range and does not change due to fluctuations in the power supply voltage and load environment. The acceleration of this speed-up method is constant.

[0005] Microstep drive control of stepper motors: Due to limitations in its own manufacturing process, such as the step angle being determined by the number of rotor teeth and the number of operating beats, but the number of rotor teeth and the number of operating beats are limited. Therefore, the step angle of a stepper motor is generally large and fixed, with low stepping resolution, lack of flexibility, vibration at low frequencies, and higher noise than other micro-motors, making physical devices prone to fatigue or damage. These drawbacks restrict the application of stepper motors to some low-requirement scenarios. For scenarios with higher requirements, only closed-loop control can be adopted, increasing the complexity of the system. These drawbacks severely limit the effective utilization of stepper motors as excellent open-loop control components. Microstep drive technology effectively overcomes these drawbacks to a certain extent. The microstep drive technology of stepper motors is a drive technology developed in the mid-1980s that can significantly improve the comprehensive performance of stepper motors. In 1982, American scholars [Scholars' names] first proposed the control method of microstepping the step angle of stepper motors at the 1982 American Incremental Motion Control Systems and Devices Conference. In the following two decades, the microstep drive of stepper motors has developed greatly and gradually matured by the 1990s. China's research on microstep drive technology started around the same time as abroad.

[0006] It had great development in the mid-1990s. It is mainly applied in fields such as industry, aerospace, robotics, precision measurement, etc., such as photoelectric theodolites for tracking satellites, military instruments, communication and radar equipment, etc. The wide application of microstepping drive technology enables the number of phases of the motor to be unrestricted by the step angle, which brings convenience to product design. Currently, in the microstepping drive technology of stepper motors, chopper constant current drive, pulse width modulation drive, and current vector constant amplitude uniform rotation drive control are adopted, greatly improving the running accuracy of stepper motors, and making stepper motors develop towards high speed and precision in medium and small power application fields. [Summary of the Invention]

[0007] The object of the present invention:

[0008] To overcome the deficiencies of the existing technology, improve the static and motion holding torque modes of the motor system, and improve the cutting accuracy and speed.

[0009] The characteristics of the present invention: Compact structure, high precision and speed, and long service life.

[0010] The key technology of the present invention: Guided by a brand-new concept for installation layout and combined with a matching algorithm can fundamentally improve the current problems.

[0011] Specific content of the invention:

[0012] The shaft power device of the present invention is used as an independent module and is used to match the 3-axis CNC machine tool under (X, Y, Z axes); the general 3-axis motion module is combined with the power indexing table of the 4th axis to form a 3 + 1 4-axis CNC machine tool; or combined with the compounding of the 4th axis to the 5th axis turntable to form a 3 + 2 5-axis CNC machine tool.

[0013] The high-rigidity dual-motor complementary power shaft device is divided into: The first case: The 4th axis complementary shaft power device (single indexing table); The second case: The 4th axis superimposed on the 5th axis complementary shaft power device (installing the indexing table on the 5th axis turntable);

[0014] *The first case: The structural characteristics of the single 4th axis complementary shaft power device; It is that 2 motors drive the indexing table on the same fixed bracket simultaneously, enabling the indexing table to perform fixed-axis rotation. A gear, turbine or pulley is fixedly installed on the indexing table shaft; The 2 motors fixed on the bracket drive the belt transmission through gears, worms or pulleys, so that the indexing table shaft drives the indexing table constrained by the bracket to rotate;

[0015] *The second case: In addition to performing the above-described dual-motor complementary-axis power processing on the index table of the 4th axis, in this case, the bracket of the index table becomes a rotatable 5th-axis turntable. The processing characteristics of the 5th-axis turntable are the same as those of the index table of the 4th axis; that is, two motors are respectively fixed on both sides or one side of the bracket to drive the 5th-axis turntable; the turntable axis of the 5th-axis turntable can be a single axis or two axes respectively extending from the shaft holes on both sides of the bracket on both sides of the turntable on the same axis. Gears, turbines or pulleys are respectively fixedly installed on the two turntable axes; the two motors are also fixed on the brackets on both sides and can drive the belt through gears, worms or pulleys, or without the above components, directly connect the shafts to make the turntable axis drive the 5th-axis turntable to rotate; furthermore, there is only one 5th-axis turntable with a turntable axis passing through the bracket. The complementary-axis power device for this single axis is the same as the description in the previous paragraph: two motors simultaneously drive the same turntable axis, and the driving connection method is the same as in the previous paragraph.

[0016] The core of the present invention lies in the installation position requirements of two superimposed torque motors: the two motors need to be installed in parallel, and the output torques are superimposed on the same rotating shaft in real time; moreover, the requirements for the relative installation positions of the two motors are step differential installation: that is, the superimposed driving phase relationship of the two stepper motors satisfies that the distance between the step angle nodes adjacent to the two motors (including under subdivision) is less than or equal to half of the step angle distance, which is equivalent to the positions and times of the two motors reaching the step angle nodes being different, forming an interlaced state.

[0017] Position and speed sensors are installed between the index table and the bracket, and between the 5th-axis turntable and the fixed bracket; the types of sensors include photoelectric sensors and electromagnetic sensors; such as including code disks, lidars, photoelectric and electromagnetic proximity switches, Hall elements, etc.

[0018] Compensation method for the high-rigidity dual-motor complementary power shaft device:

[0019] Brief description of the deep theoretical level of this compensation method:

[0020] As is well known, when a stepper motor completes one step angle, with the holding current continuously applied, the rotor is in the energy field potential well of a stable equilibrium state, and the restoring magnetic torque of the rotor is equal to zero; only when the rotor rotates slightly and deviates (less than the step angle) will it be affected by the restoring magnetic torque, and the restoring magnetic torque increases sharply with the increase of the deviation angle, and the restoring torque points to the step angle node; thus, at low speeds and node stops, a traditional independent stepper motor cannot obtain an acquired restoring torque at the step angle node (the motor stop position) and cannot resist the cutting force of the tool; in principle, it is determined that resisting the cutting force can only rely on the additional rotation deviation of the motor, sacrificing the machining accuracy; moreover, the numerical potential of the resisting torque is not large. However, the present invention uses a special motor to provide a compensating torque shape through conventional closed-loop control. The restoring torque not only responds in a timely manner, but also has a huge increase in torque value; fundamentally eradicates the industry pain point of using error deviation to obtain path regression from the principle.

[0021] Specific implementation of this compensation method:

[0022] First, clearly divide the work between 2 motors in a group: one stepper motor is used for the rotational response of the normal state and the normal path (cruising of the path); while the second motor is used as a special torque compensation motor for torque compensation regulation;

[0023] Moreover, the drive and control mode belongs to the closed-loop control mode; the detected position and speed signals of each axis are transmitted to the compensation processing circuit and the system control circuit; when there is a deviation from the predetermined path, a drive current for correction is output to drive the motor dedicated to high-stiffness compensation, and the position deviation is corrected in a timely manner to improve the accuracy level;

[0024] The high-stiffness compensation method of the present invention has three operating modes:

[0025] First, the open-loop alternating operation mode: In this mode, high-stiffness compensation of torque is not performed. Only the step angle nodes of the 2 motors are just misaligned, and each is in the middle (half: that is, 1 / 2) position of the other; the phase of the open-loop drive current pulse is also just misaligned by half a cycle; it is equivalent to halving the step angle of the original motor and doubling the path accuracy.

[0026] Second, the closed-loop alternating compensation processing mode: When the sensor does not detect a path deviation signal, it operates in the above open-loop alternating operation mode; when the (tool) path operation detected by the position and speed sensors deviates, the electronic module calculates the compensation value and outputs the drive level, and then one of the motors generates a compensation torque to execute the output of high-stiffness compensation torque to offset the operation deviation and meet the high-stiffness requirements.

[0027] Third, the closed-loop fixed division compensation processing mode: First, divide the operations of the two motors: One of the stepping motors is used to execute the operation of the predetermined path under normal conditions; while the second motor is used as a dedicated torque compensation control motor to output a return torque for compensating path deviation. According to the conventional closed-loop drive control mode, the path deviation is detected by position and speed sensors, and then the detected position and speed signals of each axis are transmitted to the compensation processing circuit and the system control circuit; when a deviation occurs compared with the predetermined path, a drive current for correction is output, so that the second dedicated motor generates a real-time driving torque to timely correct the path deviation; improving the high-stiffness response ability of the system.

[0028] Furthermore: In the high-stiffness dual-motor complementary power shaft device, the indexing plate or the fifth-axis turntable on the same fixed bracket is driven by two motors at the same time, and it is characterized in that: The complementary shaft power device is not limited to dual motors and can be extended to the cases of 3 motors, 4 motors, 5 motors, and N motors; The stepping angle nodes of N stepping motors are staggered from each other, and the sum of the N distances obtained is less than or equal to the distance of one stepping angle; and no more than N-1 motors can execute torque compensation to further improve the operating stiffness of the system. [Description of the Drawings]

[0029] The present invention will be further described below in conjunction with the preferred embodiments of the present invention with reference to the accompanying drawings:

[0030] Figure 1 Schematic diagram of a typical 5-axis mechanism.

[0031] Figure 1 A Overall view of a typical 5-axis mechanism

[0032] Figure 1 B System control and compensation processing circuit

[0033] Figure 1 C Exploded view of a typical 5-axis mechanism

[0034] Figure 2 Schematic diagram of the installation phase of the combined dual motors.

[0035] Figure 3 Schematic diagram of a typical 4-axis-like mechanism.

[0036] Figure 3 A Top view of a typical 4-axis-like mechanism

[0037] Figure 3 B Side view of a typical 4-axis-like mechanism

[0038] Figure 3 C Bottom view of a typical 4-axis-like mechanism

[0039] Figure 4 ​​​​Schematic diagram of the restoring torque magnetic tooth groove potential well curve of the stepping motor.

[0040] Figure 5 Schematic diagram showing the characteristics of the regulated torque compensation curve.

[0041] Explanation of the labels in the figure:

[0042] 1 Motor A

[0043] 2 Motor B

[0044] 3 Shaft A

[0045] 4 Bore of the 5th shaft

[0046] 5 Shaft B

[0047] 6 Exploded view

[0048] 7 System control circuit

[0049] 8 Position and speed sensor

[0050] 9 Compensation processing circuit

[0051] 10 Bracket

[0052] 11 Index plate

[0053] 12 Index plate shaft

[0054] 13 Motor C

[0055] 14 Motor D

[0056] 15 Belt

[0057] 16 4th shaft module

[0058] 17 5th axis turntable

[0059] 18 Pulley

[0060] 19 Direction of Motor A

[0061] 20 Direction of Motor B

[0062] 21 Stepping angle distribution 1 of the motor

[0063] 22 Stepping angle distribution 2 of the motor

[0064] 23 Azimuth angle of the stepping motor

[0065] 24 Stepping angle position (stable equilibrium)

[0066] 25 Middle position of the stepping angle (unstable equilibrium)

[0067] 26 Stepping angle node ​

[0068] 27 Stepper Motor Direction Indicator

[0069] 28 Offset Recovery Torque 1

[0070] 29 Offset Recovery Torque 2

[0071] 30 Conventional Single-Motor Node Torque

[0072] 31 Node Torque under Dual-Motor Compensation

[0073] 32 Node Dwell State [Detailed Implementation Manner]

[0074] As Figure 1 、 Figure 2 、 Figure 3 shown:

[0075] Figure 1 A is: Overall Diagram of a Typical 5-Axis Mechanism; Figure 1 B is: System Control and Compensation Processing Circuit; Figure 1 C is: Exploded Diagram of a Typical 5-Axis Mechanism.

[0076] Figure 3 A is: Top View of a Typical 4-Axis-Like Mechanism; Figure 3 B is: Side View of a Typical 4-Axis-Like Mechanism; Figure 3 C is: Bottom View of a Typical 4-Axis-Like Mechanism.

[0077] Figure 1 is a typical two-axis turntable, equivalent to the 4th and 5th axes in a CNC machine tool. Figure 1 C is an exploded view showing its details. The 4th-axis module (16) can be used alone to produce a 4-axis CNC machine tool; see Figure 3 it is obvious that for the 4th-axis module, the three views from top to bottom are the top view, side view, and bottom view respectively; the 5th-axis hole (4) is for a tight fit with the 5th-axis motor shaft; the indexing plate shaft (12) is connected to the pulley (18).

[0078] During installation, the direction of motor B (20) is not parallel to the direction of motor A (19), causing the stepping nodes of the two motors not to coincide.

[0079] The indexing plate (11) is driven by the motor A (1) and the motor B (2) fixed on both sides of the bracket (10), and the shaft A (3) and the shaft B (5) are on the same motor axis; the motor C (13) and the motor D (14) drive the pulley (18) through the belt (15) to drive the fifth-axis turntable (17) to rotate; there are strict requirements for the relative installation positions of each group of motors; first, for the installation of the motor A (1) and the motor B (2); and there are clear requirements for the installation phase between the motor C (13) and the motor D (14): it is required that the two stepping motor angles (including the stepping angles under microstepping) are the same; the starting points of the stepping angles fall into the middle positions of the stepping angles of the other motor.

[0080] Between the indexing plate (11) and the bracket (10), and between the fifth-axis turntable (17) and the indexing plate (11), position and speed sensors (8) are installed; in the closed-loop control mode; it is necessary to use the position and speed sensors (8) to detect the rotation positions and the current rotation speed signals of the indexing plate (11) and the fifth-axis turntable (17); these position and speed information are transmitted to the compensation processing circuit (9) and the system control circuit (7); when there is a deviation from the predetermined path, a corrected drive current is output, so that the motor A (1) and the motor B (2), or the motor C (13) and the motor D (14) can correct the position deviation in time; improving the accuracy level.

[0081] As Figure 4 、 Figure 5 shown:

[0082] Figure 4 In the following figure, the horizontal axis represents the angular position of the stepping motor rotor, and the vertical axis represents the magnitude of the restoring magnetic torque received by the rotor at the angular position near the stepping angle. When the stepping motor is in the self-locking state, if an external force forces the motor shaft to deviate from the stepping angle node position, when the rotor is at the stepping angle position (24), it is in stable equilibrium, equivalent to being in an energy field potential well, and the restoring magnetic torque received is equal to zero; but when the rotor deviates from the above stable equilibrium point, the rotor will be affected by the restoring magnetic torque. As the deviation angle increases, the restoring magnetic torque will increase sharply, causing the rotor to have a tendency to return to the equilibrium position of the stepping angle; when at the middle position (25) of the stepping angle, the restoring magnetic torque will be even greater; that is, in the node dwell state (32) self-locking state, the restoring torque is opposite to the angular displacement of the motor shaft (at least within half a stepping angle) and the direction of the restoring torque, as Figure 4 shown by the offset restoring torque 1 (28) and the offset restoring torque 2 (29) of the restoring force display torque value.

[0083] The stepping angles of two motors in the same group are the same, as indicated by motor stepping angle distribution 1 (21) and motor stepping angle distribution 2 (22). The stopping angular positions of the rotor stepping are stepping angle nodes (26), and the motor rotor can stop at these angular positions. If the structure of one of the stepping motors is rotated by an angle φ, it is in the position of the relative azimuth angle (23) of the stepping motor, as indicated by the stepping motor direction identifier (27).

[0084] In summary, in the driving state of a traditional single motor, the potential value of the recoverable torque obtained when the motor travels at a higher speed is small and fluctuating. At low speeds and node stops, the recoverable torque is even smaller, and the recoverable torque can only be obtained with a certain angular displacement deviation. See the conventional single motor node torque (30).

[0085] However, in the dual-motor compensation state of the present invention, the value and potential of the recoverable torque have a qualitative leap. In addition to compensating for the fluctuation of the recoverable torque potential, even at low speeds and node stops, the recoverable torque is very large, and the recoverable torque can be obtained without any angular displacement deviation. See the node torque (31) under dual-motor compensation.

Claims

1. High-rigidity dual-motor complementary power axis device, divided into a 4th-axis complementary axis power device with a single indexing plate; and a 4th-axis superimposed 5th-axis complementary axis power device; this axis power device is used as an independent module to match the 4th-axis complementary axis power device including a general 3-axis motion module to form a 3+1 4-axis CNC machine tool; or to match the 4th-axis superimposed 5th-axis complementary axis power device to form a 3+2 5-axis CNC machine tool; That The characteristics are: The fourth axis complementary axis power device of a single indexing plate; two motors simultaneously drive the indexing plate on the same fixed bracket, so that the indexing plate can rotate on a fixed axis, and a gear, turbine or pulley is fixedly installed on the indexing plate shaft; the two motors fixed on the bracket drive the belt transmission through gears, worms or pulleys, so that the indexing plate shaft drives the indexing plate constrained by the bracket to rotate; The 4th axis is superimposed on the 5th axis complementary axis power device; the bracket of the complementary axis power device of the 4th axis indexing disk is used as the 5th axis turntable, and the processing characteristics of the 5th axis turntable are the same as those of the 4th axis indexing disk; two motors are respectively fixed on both sides or one side of the bracket to drive the 5th axis turntable; the turntable shaft of the 5th axis turntable can be a single axis or two sides of the turntable on the same axis, and two shafts extend out of the shaft holes on both sides of the bracket respectively, and gears, turbines or pulleys are fixedly installed on the two turntable shafts; two motors are also fixed on the brackets on both sides, and the belts can be driven by gears, worms or pulleys, or the above components are not used, and the turntable shaft drives the 5th axis turntable to rotate directly; in addition, the 5th axis turntable can be provided with only a single turntable shaft, and the same turntable shaft is still driven by two motors at the same time, and the driving connection method is the same as the complementary axis power device of the 4th axis indexing disk; The installation position requirements of the two superimposed torque motors are: the two motors are installed in parallel, and the output torque is superimposed on the same shaft in real time; and the relative installation position requirements of the two motors are step differential installation: that is, the superimposed drive phase relationship of the two stepper motors satisfies: the distance between the adjacent step angle nodes of the two motors is less than or equal to the distance of half a step angle, which is equivalent to the position and time of the two motors reaching the step angle node being different, forming a state of mutual insertion; Position and speed sensors are installed between the indexing plate and the bracket, and between the 5th axis turntable and the fixed bracket; the types of sensors include photoelectric sensors and electromagnetic sensors.

2. The high-rigidity dual-motor complementary power shaft device as claimed in claim 1, wherein the two motors simultaneously drive the indexing plate or the fifth-axis turntable on the same fixed bracket, characterized in that: The complementary shaft power device is not limited to dual motors, but can be expanded to 3 motors, 4 motors, 5 motors, and N motors; the step angle nodes of the N stepper motors are staggered with each other, and the sum of the N distances obtained is less than or equal to the distance of one step angle; and no more than N-1 motors can perform torque compensation.

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