Dual motor control method for a machine tool spindle

Abstract

The application provides a double-motor control method for a machine tool spindle, which comprises the following operation steps of a controller, a motor A and a motor B: a, initialization of a control system of the controller; b, the controller acquires required power P of the machine tool spindle in real time, and judges the relationship between P and set power P1 of the motor A, set power P2 of the motor B and maximum power P3; c, the control system collects temperature T1 of the motor A, compares T1 with a set value K, and proceeds according to steps S1 and S2; d, the control system collects temperature T1 of the motor A, compares T1 with the set value K, and proceeds according to steps J1 and J2; e, the system monitors the temperature of the motor A and the motor B, judges whether the temperature of the two exceeds the respective temperature limit value, if the temperature of any motor exceeds the limit, the motor A and the motor B stop, otherwise, returns to step b; when the spindle works, the efficiency of the motor is improved, the energy consumption of the motor is reduced and the temperature of the motor is controlled.

Description

Technical Field

[0001] This invention belongs to the field of machine tools, and particularly relates to a dual-motor control method for a machine tool spindle. Background Technology

[0002] The spindle of a machine tool is generally used to hold the corresponding workpiece in a fixture. The spindle is driven to rotate by a motor, allowing the workpiece to be cut by a tool on one side of the spindle. The power source for the spindle is a motor, and existing machine tool spindles generally use independent motors for driving, including DC permanent magnet synchronous motors and AC asynchronous motors. The connection methods between the motor and the spindle include flange connection, gear transmission, or electric spindle drive where the spindle acts as the motor rotor. However, the existing method of driving machine tool spindles with independent motors has disadvantages. For example, the motor temperature can become too high when operating at continuous high power, causing irreversible demagnetization of the permanent magnets in DC permanent magnet synchronous motors; AC asynchronous motors are generally less efficient than DC permanent magnet synchronous motors and consume more power; AC asynchronous motors only reach peak efficiency when their output power is above 70% of their maximum power; each type of motor has its high-efficiency operating range, and when the power required by the spindle exceeds the output power of the drive motor within its high-efficiency operating range, it increases the motor's energy consumption and, for AC asynchronous motors, reduces their power factor, adversely affecting the power grid. Therefore, it is necessary to improve the existing motor drive method of machine tool spindles to reduce motor energy consumption, improve power factor and control motor temperature. Summary of the Invention

[0003] (a) Technical problems to be solved

[0004] To address the aforementioned technical problems, the purpose of this invention is to provide a dual-motor control method for machine tool spindles. By utilizing the characteristics of DC permanent magnet synchronous motors and AC asynchronous motors, the method improves motor efficiency, reduces motor energy consumption, and controls motor temperature during spindle operation.

[0005] (II) Technical Solution

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This invention provides a dual-motor control method for a machine tool spindle, comprising the following operating steps of a controller, motor A, and motor B:

[0008] a. Control system initialization of the controller;

[0009] b. The controller acquires the power P required by the machine tool spindle in real time and determines the relationship between P and the set power P1 of motor A, the set power P2 of motor B, and the maximum power P3; if P≤P1, proceed to step c; otherwise, proceed to step d.

[0010] c. The control system collects the temperature T1 of motor A, compares T1 with the set value K, and proceeds according to steps S1 and S2:

[0011] S1. If T1 < K, only motor A operates with an output power of P; if T1 ≥ K and P < P2, the output power of motor B is P2 and the output power of motor A is P - P2; if T1 ≥ K, P ≥ P2, and P < P3, only motor B operates with an output power of P; if T1 ≥ K, P ≥ P2, and P ≥ P3, the output power of motor B is P2 and the output power of motor A is P - P2.

[0012] S2. Proceed to step e.

[0013] d. The control system collects the temperature T1 of motor A, compares T1 with the set value K, and proceeds according to steps J1 and J2:

[0014] J1. If T1 < K, the output power of motor A is P1 and the output power of motor B is P - P1; if T1 ≥ K and P < P2, the output power of motor A is P1 and the output power of motor B is P - P1; if T1 ≥ K, P ≥ P2, and P < P3, only motor B operates with an output power of P; if T1 ≥ K, P ≥ P2, and P ≥ P3, the output power of motor B is P2 and the output power of motor A is P - P2.

[0015] J2. Proceed to step e.

[0016] e. The system monitors the temperatures of motor A and motor B, determines whether either exceeds its respective temperature limit. If the temperature of any motor is over the limit, motors A and B stop; otherwise, return to step b.

[0017] As a preference, |P - P2| < P1.

[0018] As a preference, |P - P1| > P2.

[0019] As a preference, the set value K is set to 80% of the upper temperature limit of motor A.

[0020] As a preference, P1 is 80% of the maximum power of motor A.

[0021] As a preference, P2 is 70% of the maximum power of motor B.

[0022] (III) Beneficial effects

[0023] The present invention provides a dual - motor control method for a machine tool spindle, having the following beneficial effects:

[0024] 1. The control method of the present invention utilizes the characteristics of high efficiency and low power consumption of the DC permanent magnet synchronous motor, and preferentially uses the DC permanent magnet synchronous motor to reduce power consumption. It also utilizes the high temperature resistance characteristics of the AC asynchronous motor and the characteristics of higher efficiency and higher power factor when outputting high power, and uses more power sharing to reduce the load of the DC permanent magnet synchronous motor, preventing the DC permanent magnet synchronous motor from exceeding the temperature limit due to excessive power output or long-term operation, and thus causing irreversible demagnetization of the permanent magnet.

[0025] 2. If the power P required by the machine tool spindle can satisfy |P - P2| < P1, then when the output power of motor A is P - P2, motor A is made to operate within the high-efficiency working range.

[0026] 3. If the power P required by the machine tool spindle can satisfy |P - P1| > P2, then when the output power of motor B is P - P1, motor B is made to operate within the high-efficiency and high-power factor working range.

[0027] 4. The set value K is set to 80% of the upper temperature limit value of motor A, which can not only enable motor A to perform temperature control in advance before reaching the temperature limit, but also enable motor A to continue to function in a way of operating with a smaller power or for a shorter time after the temperature exceeds the set value K.

[0028] 5. P1 is set to 80% of the maximum power of motor A, which can enable motor A to output the maximum power within the high-efficiency operating range.

[0029] 6. P2 is set to 70% of the maximum power of motor B, which can enable motor B to operate within the high-efficiency and high-power factor operating range as much as possible, not only reducing the power consumption of motor B, but also reducing the adverse impact of motor B on the power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the dual-motor drive scheme for the machine tool spindle of the present invention;

[0031] Figure 2 It is a schematic diagram of the dual-motor control method for the machine tool spindle of the present invention.

[0032] In the figure: 1. Spindle; 2. Bearing; 3. Motor A; 4. Driving gear A; 5. Driven gear; 6. Driving gear B; 7. Motor B. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0034] As shown Figure 1 in the figure, in this invention, the main shaft 1 of the machine tool is supported on the bearing 2. A driven gear 5 is fixedly connected to one end of the main shaft 1. On both sides of the main shaft 1, a motor A and a motor B are respectively provided. The rotor ends of the motor A and the motor B are respectively connected with a driving gear A and a driving gear B. The driving gear A and the driving gear B are respectively meshed with the driven gear 5. The motor A is a DC permanent magnet synchronous motor, and the motor B is an AC asynchronous motor.

[0035] This invention further includes a controller, which is respectively connected with the motor A and the motor B in a signal connection manner for controlling the working process of the motor A and the motor B. The controller is also connected with the computer of the machine tool in a signal connection manner for obtaining the real-time power demand P of the main shaft of the machine tool. When the output power of the motor A (i.e., the DC permanent magnet synchronous motor) is within the range of 20% to 80% of the maximum power, the efficiency is greater than or equal to 90%. Define 80% of the maximum power of the motor A as P1. When the output power of the motor B (AC asynchronous motor) is above 70% of the maximum power, its efficiency is greater than or equal to 80% and the power factor is greater than or equal to 0.85. Define 70% of the maximum power of the motor B as P2, and define the maximum output power of the motor B as P3. Temperature sensors are respectively provided on the motor A and the motor B for detecting the real-time temperature of the corresponding motor and transmitting the temperature signal to the controller. The motor A has a temperature set value K for controlling the process. The motor A and the motor B respectively have a temperature upper limit value. When the temperature exceeds the upper limit value, the corresponding motor needs to stop immediately for cooling to prevent damage to the motor.

[0036] When the motor operates in a high-efficiency state, its energy consumption is lower, the heat generation is smaller, and when the AC asynchronous motor operates in a high-efficiency state, its power factor is higher and the impact on the power grid is smaller.

[0037] Therefore, a dual-motor control method for the main shaft of a machine tool designed by this invention includes the following steps:

[0038] 1. Initialize the control system of the controller.

[0039] 2. The control system of the controller communicates with the computer of the machine tool to obtain the power P required by the main shaft of the machine tool in real time, and judges the relationship between P and P1; if P ≤ P1, enter step 3; if P > P1, enter step 4.

[0040] 3. The control system collects the temperature T1 of the motor A and judges the relationship between T1 and the temperature set value K;

[0041] (1) If T1 < K, only the motor A works, and its output power is P;

[0042] (2) If T1 ≥ K, judge the relationship between P and P2;

[0043] ① If P < P2, the output power of motor B is P2, and the output power of motor A is P - P2;

[0044] ② If P ≥ P2, then judge the relationship between P and P3. If P < P3, only motor B works and its output power is P; if P ≥ P3, the output power of motor B is P2, and the output power of motor A is P - P2;

[0045] (3) Enter step 5.

[0046] 4. The control system collects the temperature T1 of motor A and judges the relationship between T1 and the temperature set value K;

[0047] (1) If T1 < K, the output power of motor A is P1, and the output power of motor B is P - P1;

[0048] (2) If T1 ≥ K, then judge the relationship between P and P2;

[0049] ① If P < P2, the output power of motor A is P1, and the output power of motor B is P - P1;

[0050] ② If P ≥ P2, then judge the relationship between P and P3. If P < P3, only motor B works and its output power is P; if P ≥ P3, the output power of motor B is P2, and the output power of motor A is P - P2;

[0051] (3) Enter step 5.

[0052] 5. The system monitors the temperatures of motor A and motor B and judges whether they exceed their respective temperature limits. If the temperature of any motor is over the limit, motor A and motor B stop; otherwise, return to step 2.

[0053] The control method of the present invention is characterized in that:

[0054] In step 2, by judging the relationship between P and P1, when P ≤ P1, motor A is preferentially made to work to give full play to its power output ability in the high-efficiency range; when P > P1, due to the reduction of the efficiency of motor A and in order to avoid the temperature of motor A exceeding the limit at high power, motor B is made to share a part of the output power.

[0055] In step 3, by judging the relationship between the temperature T1 of motor A and the set value K, it is determined whether motor A works alone to prevent the motor temperature from continuously rising above the limit. As a preference, the set value K is set to 80% of the upper limit value of the temperature of motor A. By judging the relationship between P and P2, P3, if P < P2, let motor B work at P2, which can improve its efficiency and power factor. At this time, let motor A output a negative torque (i.e., negative power) to help motor B work in a high-efficiency state and reduce the output power of motor A and prevent the temperature of motor A from exceeding the limit. If P2 ≤ P < P3, then the output power P of motor B is exactly within its high-efficiency and high-power-factor working range. If P > P3, then the output power of motor B is set to P2 to keep it working efficiently, and at the same time, motor A provides the remaining power P - P2 to reduce the output power of motor A and prevent the temperature of motor A from exceeding the limit. As a preference, when selecting a motor during the machine tool design process, if the power P required by the machine tool spindle can satisfy |P - P2| < P1, then motor A not only assists motor B in working but also enables motor A to be within a high-efficiency working range, and motor A is also in a low-load working state.

[0056] In step 4, by judging the relationship between the temperature T1 of motor A and the set value K, it is determined whether motor A outputs power; if T1 < K, then the output power of motor A is P1 and the output power of motor B is P - P1, so that motor A outputs the maximum power within the high-efficiency range; as a preference, when selecting a motor during the machine tool design process, if the power P required by the machine tool spindle can satisfy |P - P1| > P2, then motor B not only assists motor A in working but also enables motor B to be within the high-efficiency and high-power-factor working range. If T1 ≥ K, by judging the relationship between P and P2, P3, when P < P2, the output power of motor A is P1 and the output power of motor B is P - P1, ensuring that motor A outputs the maximum power within the high-efficiency range. When P2 ≤ P < P3, then the output power P of motor B is exactly within its high-efficiency and high-power-factor working range; when P > P3, then the output power of motor B is P2 to keep it working efficiently, and at the same time, motor A provides the remaining power P - P2; similarly, as a preference, if |P - P2| < P1, motor A is in a high-efficiency working range and a low-load working state.

[0057] DC permanent magnet synchronous motors (PMSMs) are more sensitive to temperature and more significantly affected by it than AC asynchronous motors due to the high-temperature demagnetization phenomenon. Therefore, the control method of this invention uses the temperature control of the PMSM as the primary condition. When the temperature of motor A is below a set value K, motor A is prioritized to output its maximum power P1 at high efficiency, thereby improving the overall efficiency of the two motors. When the temperature of motor A is above the set value K, motor B is prioritized to operate, sharing the power of motor A and reducing the output power of motor A to prevent demagnetization due to excessive temperature. The entire control process involves not only the temperature control of motor A but also the efficiency of motors A and B during operation, as well as the power factor of motor B, achieving improved motor efficiency, reduced motor energy consumption, and temperature control during spindle operation. This invention utilizes the high efficiency characteristics of the PMSM to reduce power consumption, and also leverages the high-temperature resistance and higher efficiency of the AC asynchronous motor at high power output to share the load of the PMSM and prevent demagnetization due to excessive temperature.

[0058] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A dual-motor control method for a machine tool spindle, wherein the dual motors are motor A, which is a DC permanent magnet synchronous motor, and motor B, which is an AC asynchronous motor, characterized in that... The following operating steps for a controller, motor A, and motor B: a. Initialize the control system of the controller; b. The controller obtains the required power P of the machine tool spindle in real time and determines the relationship between P and the set power P1 of motor A, the set power P2 of motor B, and the maximum power P3; if P ≤ P1, proceed to step c, otherwise proceed to step d; c. The control system collects the temperature T1 of motor A, compares T1 with the set value K, and proceeds according to steps S1 and S2: S1. If T1 < K, only motor A operates with an output power of P; if T1 ≥ K and P < P2, the output power of motor B is P2 and the output power of motor A is P - P2; if T1 ≥ K and P ≥ P2, P < P3, only motor B operates with an output power of P; if T1 ≥ K and P ≥ P2, P ≥ P3, the output power of motor B is P2 and the output power of motor A is P - P2; S2. Proceed to step e; d. The control system collects the temperature T1 of motor A, compares T1 with the set value K, and proceeds according to steps J1 and J2: J1. If T1 < K, the output power of motor A is P1 and the output power of motor B is P - P1; if T1 ≥ K and P < P2, the output power of motor A is P1 and the output power of motor B is P - P1; if T1 ≥ K and P ≥ P2, P < P3, only motor B operates with an output power of P; if T1 ≥ K and P ≥ P2, P ≥ P3, the output power of motor B is P2 and the output power of motor A is P - P2; J2. Proceed to step e; e. The system monitors the temperatures of motor A and motor B and determines whether either exceeds its respective temperature limit. If the temperature of any motor is over the limit, motor A and motor B stop; otherwise, return to step b.

2. The dual-motor control method for a machine tool spindle according to claim 1, characterized in that: |P - P2| < P1.

3. The dual-motor control method for a machine tool spindle according to claim 1, characterized in that: |P - P1| > P2.

4. A dual-motor control method for a machine tool spindle according to any one of claims 1-3, characterized in that: The set value K is set to 80% of the upper temperature limit of motor A.

5. A dual-motor control method for a machine tool spindle according to any one of claims 1-3, characterized in that: P1 is 80% of the maximum power of motor A.

6. A dual-motor control method for a machine tool spindle according to any one of claims 1-3, characterized in that: P2 is 70% of the maximum power of motor B.

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