System and method for controlling squeeze wheels of tennis ball machine

Abstract

A system and method for controlling squeeze wheels of a tennis ball machine. The system comprises a main control module (11), an upper wheel electric motor module (12) and a lower wheel electric motor module (13), wherein the main control module (11) sends a PWM signal having a full duty cycle to each of the upper wheel electric motor module (12) and the lower wheel electric motor module (13); the upper wheel electric motor module (12) and the lower wheel electric motor module (13) respectively measure an operation current and rotation speed of a squeeze upper wheel electric motor (123) and those of a squeeze lower wheel electric motor (133) and send same to the main control module (11); and on the basis of the currents, the main control module (11) outputs, to the upper wheel electric motor module (12) and the lower wheel electric motor module (13) in a PID control mode, PWM signals having required duty cycles, and on the basis of the rotation speeds, the main control module (11) correspondingly determines whether the squeeze upper wheel electric motor (123) and the squeeze lower wheel electric motor (133) have been started or accelerated to target rotation speeds, so as to adjust the PWM signals output to the upper wheel electric motor module (12) and the lower wheel electric motor module (13).

Description

Tennis ball serving machine ball squeezing wheel control system and control method

[0001] This application claims priority to the Chinese patent application No. 202411367227.X, filed on September 29, 2024, with the Chinese Patent Office, the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application belongs to the technical field of sports equipment, for example, relates to a tennis ball serving machine ball squeezing wheel control system and control method. BACKGROUND

[0003] Tennis ball serving machines, as an important device to improve the efficiency of tennis training, are widely used in professional training and daily practice of amateur enthusiasts. In order to simulate real game situations, modern tennis ball serving machines not only need to be able to launch tennis balls at different speeds, but also need to have the ability to adjust the rotation of the ball. This requires the internal drive motor to have enough torque to achieve high-speed serving (usually more than 100 kilometers per hour (km / h)) and to quickly adjust the speed in a short time to change the speed and rotation type of the ball.

[0004] Most high-performance tennis ball serving machines on the market currently use direct current brush motors as power sources. Such motors are known for their high power density and good speed regulation performance. However, since these motors consume a very large current when starting, the starting current is about 20 amperes (A), which poses a considerable challenge to the power supply system under the condition of rated voltage. Especially considering that most tennis ball serving machines are deployed in outdoor environments and tend to use rechargeable lithium batteries as power sources, this further limits the battery capacity and discharge capability that can be used. Generally, due to portability constraints, the selected lithium battery capacity is about 5000 milliampere-hours (mAh), supporting a maximum 3 times rate (C) discharge rate, i.e., a peak current output of 15 A. Therefore, how to effectively manage the large current during the starting phase becomes one of the key problems in design.

[0005] To address the above challenges, a common strategy currently adopted is to perform soft start processing on the motor through pulse width modulation (PWM) technique. The related practice is to provide a PWM signal with a small duty cycle (e.g. 20%) to the motor at the initial stage of start, so as to limit the start current level; then gradually increase the duty cycle of the PWM signal as the motor gradually accelerates until the target running state is reached. Although this method helps to alleviate the adverse effects of large current impact, it also has obvious disadvantages: firstly, the start process becomes quite slow, and it usually takes up to 10 to 20 seconds to accelerate from static to the preset speed; secondly, when frequent switching between different working modes is required (such as quickly increasing from low speed 20km / h to high speed 100km / h or vice versa), the overall response speed is not ideal due to the gradual control mode, which is difficult to meet the demand for flexible adjustment in actual application. SUMMARY

[0006] The application provides a tennis ball serving machine ball squeezing wheel control system and control method, which can realize fast start and fast switching of the ball squeezing wheel motor, and enhance user experience.

[0007] According to a first aspect of the embodiments of the application, the application provides a tennis ball serving machine ball squeezing wheel control system, which comprises a main control module, an upper wheel motor module and a lower wheel motor module connected with the main control module;

[0008] The main control module is configured to send a full duty cycle PWM signal to the upper wheel motor module and the lower wheel motor module, so as to control the ball squeezing upper wheel motor in the upper wheel motor module and the ball squeezing lower wheel motor in the lower wheel motor module to start or accelerate;

[0009] The upper wheel motor module is configured to detect the current and speed of the ball squeezing upper wheel motor and send them to the main control module, and the lower wheel motor module is configured to detect the current and speed of the ball squeezing lower wheel motor and send them to the main control module;

[0010] The main control module is configured to output a PWM signal with a required duty cycle to the upper wheel motor module according to the received current of the ball squeezing upper wheel motor in a PID control mode, so as to drive the ball squeezing upper wheel motor to run; and the main control module is also configured to output a PWM signal with a required duty cycle to the lower wheel motor module according to the received current of the ball squeezing lower wheel motor in a PID control mode, so as to drive the ball squeezing lower wheel motor to run;

[0011] The main control module is further configured to determine whether the upper ball extruding wheel motor has started or accelerated to the target speed of the upper wheel motor according to the received speed of the upper ball extruding wheel motor, and determine whether the lower ball extruding wheel motor has started or accelerated to the target speed of the lower wheel motor according to the received speed of the lower ball extruding wheel motor, and then adjust the PWM signals output to the upper wheel motor module and the lower wheel motor module according to the determination results.

[0012] In some embodiments, the upper wheel motor module comprises a first auxiliary control module, a first brake module, an upper ball extruding wheel motor, an upper wheel current detection module and an upper wheel speed encoder.

[0013] The first auxiliary control module is connected with the main control module and configured to receive the PWM signal sent by the main control module; the first auxiliary control module is connected with the first brake module and the upper ball extruding wheel motor and configured to control the operation of the upper ball extruding wheel motor and control the deceleration braking of the upper ball extruding wheel motor through the first brake module; the upper wheel current detection module is configured to detect the operating current of the upper ball extruding wheel motor and send it to the main control module; and the upper wheel speed encoder is configured to detect the speed of the upper ball extruding wheel motor and send it to the main control module.

[0014] In some embodiments, the lower wheel motor module comprises a second auxiliary control module, a second brake module, a lower ball extruding wheel motor, a lower wheel current detection module and a lower wheel speed encoder.

[0015] The second auxiliary control module is connected with the main control module and configured to receive the PWM signal sent by the main control module; the second auxiliary control module is connected with the second brake module and the lower ball extruding wheel motor and configured to control the operation of the lower ball extruding wheel motor and control the deceleration braking of the lower ball extruding wheel motor through the second brake module; the lower wheel current detection module is configured to detect the operating current of the lower ball extruding wheel motor and send it to the main control module; and the lower wheel speed encoder is configured to detect the speed of the lower ball extruding wheel motor and send it to the main control module.

[0016] In some embodiments, the first auxiliary control module is implemented by an H half-bridge circuit, the first brake module is implemented by a brake circuit, and the upper wheel current detection module is implemented by a sampling and amplification circuit.

[0017] In some embodiments, the H half-bridge circuit comprises a first field effect transistor and a second field effect transistor; the gate of the first field effect transistor is connected with the first IO port of the main control module, the drain of the first field effect transistor is connected with the positive pole of a motor power supply, the negative pole of the motor power supply is grounded, the source of the first field effect transistor is connected with the first end of the upper ball extruding wheel motor and the drain of the second field effect transistor; the gate of the second field effect transistor is connected with the second IO port of the main control module, and the source of the second field effect transistor is connected with the second end of the upper ball extruding wheel motor.

[0018] In some embodiments, the braking circuit comprises a third field effect tube and a braking resistor, a gate of the third field effect tube is connected with a third IO port of the master module, a drain of the third field effect tube is connected with a source of the first field effect tube through the braking resistor, and a source of the third field effect tube is grounded.

[0019] In some embodiments, the sampling and amplifying circuit comprises a sampling resistor and a current amplifier, a first end of the sampling resistor is connected with a source of the second field effect tube, and a second end of the sampling resistor is grounded; two input ports of the current amplifier are respectively connected with two ends of the sampling resistor, and an output port of the current amplifier is connected with a fourth IO port of the master module.

[0020] In some embodiments, the master module is configured with a starting program and an accelerating program, and the starting program and the accelerating program are:

[0021] outputting full-duty-cycle PWM signals to the upper wheel motor module and the lower wheel motor module to control the ball squeezing upper wheel motor and the ball squeezing lower wheel motor to start or start accelerating;

[0022] receiving running currents of the ball squeezing upper wheel motor detected by the upper wheel current detection module and running currents of the ball squeezing lower wheel motor detected by the lower wheel current detection module;

[0023] controlling the running currents of the ball squeezing upper wheel motor and the ball squeezing lower wheel motor in a PID control mode according to the received running currents, and outputting PWM signals with required duty cycles to keep the running currents at preset target currents;

[0024] outputting the PWM signals with required duty cycles to the upper wheel motor module and the lower wheel motor module to control the running of the ball squeezing upper wheel motor and the ball squeezing lower wheel motor by using the PWM signals with required duty cycles;

[0025] obtaining the rotating speeds of the ball squeezing upper wheel motor and the ball squeezing lower wheel motor detected by the upper wheel speed encoder and the lower wheel speed encoder, and exiting the starting or accelerating program in response to judging that the obtained rotating speeds reach a first target rotating speed.

[0026] In some embodiments, the master module is configured with a deceleration braking program, and the deceleration braking program is:

[0027] turning off the motor power supply, controlling the first braking module and the second braking module to be turned on, and braking the current of the ball squeezing upper wheel motor and the current of the ball squeezing lower wheel motor through the first braking module and the second braking module respectively;

[0028] obtaining the rotating speeds of the ball squeezing upper wheel motor and the ball squeezing lower wheel motor detected by the upper wheel speed encoder and the lower wheel speed encoder, and exiting the deceleration braking program in response to judging that the obtained rotating speeds reach a second target rotating speed.

[0029] According to a second aspect of the embodiments of the present application, the present application further provides a tennis ball serving machine extrusion ball wheel control method based on the tennis ball serving machine extrusion ball wheel control system according to any of the above embodiments, the method comprising a starting process, an acceleration process and a deceleration braking process.

[0030] The starting process and the acceleration process comprise:

[0031] The main control module outputs full-duty PWM signals to the upper wheel motor module and the lower wheel motor module to control the extrusion upper wheel motor in the upper wheel motor module and the extrusion lower wheel motor in the lower wheel motor module to start or start accelerating;

[0032] The upper wheel current detection module detects the running current of the extrusion upper wheel motor, and the lower wheel current detection module detects the running current of the extrusion lower wheel motor, and feeds back the detected running current to the main control module;

[0033] The main control module outputs PWM signals with required duty ratios to the upper wheel motor module and the lower wheel motor module according to the received running current in a PID control mode;

[0034] The first auxiliary control module in the upper wheel motor module and the second auxiliary control module in the lower wheel motor module control the running of the extrusion upper wheel motor and the extrusion lower wheel motor according to the received PWM signals with required duty ratios;

[0035] The upper wheel speed detection encoder detects the rotating speed of the extrusion upper wheel motor, and the lower wheel speed detection encoder detects the rotating speed of the extrusion lower wheel motor, and feeds back the detected rotating speed to the main control module;

[0036] The main control module compares the acquired rotating speed with a preset first target rotating speed, and exits the starting or acceleration program in response to the acquired rotating speed reaching the first target rotating speed;

[0037] The deceleration braking process comprises:

[0038] The main control module controls the first brake module and the second brake module to be opened through the first auxiliary control module and the second auxiliary control module respectively to brake the extrusion upper wheel motor and the extrusion lower wheel motor;

[0039] The upper wheel speed detection encoder detects the rotating speed of the extrusion upper wheel motor, and the lower wheel speed detection encoder detects the rotating speed of the extrusion lower wheel motor, and feeds back the detected rotating speed to the main control module;

[0040] The main control module compares the acquired rotating speed with a preset second target rotating speed, and exits the deceleration braking program in response to the acquired rotating speed reaching the second target rotating speed.

[0041] It should be appreciated that the foregoing general description and the following detailed description are only exemplary and explanatory. BRIEF DESCRIPTION OF DRAWINGS

[0042] Fig. 1 is a structural block diagram of a tennis ball serving machine squeeze ball wheel control system according to some embodiments of the present application;

[0043] Fig. 2 is a schematic diagram of a control braking circuit in a tennis ball serving machine squeeze ball wheel control system according to some embodiments of the present application;

[0044] Fig. 3 is a flow chart of a start-up program and an acceleration program of a master control module in a tennis ball serving machine squeeze ball wheel control system according to some embodiments of the present application;

[0045] Fig. 4 is a flow chart of a deceleration braking program of a master control module in a tennis ball serving machine squeeze ball wheel control system according to some embodiments of the present application.

[0046] BRIEF DESCRIPTION OF DRAWINGS 11, master control module; 12, upper wheel motor module; 121, first auxiliary control module; 122, first braking module; 123, squeeze ball upper wheel motor; 124, upper wheel current detection module; 125, upper wheel speed encoder; 13, lower wheel motor module; 131, second auxiliary control module; 132, second braking module; 133, squeeze ball lower wheel motor; 134, lower wheel current detection module; 135, lower wheel speed encoder; MOS1, first field effect transistor; MOS2, second field effect transistor; MOS3, third field effect transistor; PWM_H, first IO port; PWM_L, second IO port; SW1, third IO port; ADC1, fourth IO port; R1, braking resistor; R2, sampling resistor; AMP1, current amplifier. DETAILED DESCRIPTION

[0047] The illustrative embodiments of the present application and their description serve only as examples of embodiments of the present application. In addition, the same or similar components / elements are denoted by the same or similar reference numbers throughout the drawings and the embodiments.

[0048] As used herein, the terms "first", "second", etc. are used only to distinguish one element or operation from another, and do not necessarily have a "first", "second" etc. meaning in all cases.

[0049] As used herein, the terms "comprise", "include", "have", "contain", etc. are open- ended and mean "including but not limited to".

[0050] As used herein, "and / or" includes any or all combinations of the associated items.

[0051] As used herein, "a plurality" includes "two" and "more than two"; as used herein, "a plurality of groups" includes "two groups" and "more than two groups".

[0052] Some of the words used to describe the present application will be discussed below or elsewhere in this specification to provide additional guidance to those skilled in the art on the description related to the present application.

[0053] Although the related technical solutions can solve the problem of excessive motor starting current of the tennis ball serving machine to a certain extent, they also introduce new bottlenecks, especially in application scenarios that pursue higher operation flexibility and faster response speed. Therefore, it is particularly important to develop a new generation of tennis ball serving machine extrusion ball wheel control system and control method that can not only guarantee efficient energy conversion but also quickly respond to changing demands.

[0054] The tennis ball serving machine extrusion ball wheel control system and control method provided by the present application will be described below in conjunction with FIGS. 1-4.

[0055] In some embodiments, the extrusion ball wheel is composed of an upper extrusion ball wheel and a lower extrusion ball wheel arranged symmetrically up and down, which drives the tennis ball to be launched by generating friction force through relative rotation.

[0056] As shown in FIG. 1, the tennis ball serving machine extrusion ball wheel control system provided by the embodiments of the present application includes a main control module 11, an upper wheel motor module 12 connected to the main control module 11, and a lower wheel motor module 13 connected to the main control module 11. Among them, the main control module 11 is configured to send a full-duty PWM signal to the upper wheel motor module 12 and the lower wheel motor module 13 to control the extrusion upper wheel motor 123 in the upper wheel motor module 12 and the extrusion lower wheel motor 133 in the lower wheel motor module 13 to start or accelerate; the upper wheel motor module 12 is configured to detect the current and speed of the extrusion upper wheel motor 123 and send it to the main control module 11, and the lower wheel motor module 13 is configured to detect the current and speed of the extrusion lower wheel motor 133 and send it to the main control module 11.

[0057] The main control module 11 is configured to output a PWM signal with a required duty ratio to the upper wheel motor module 12 to drive the extrusion upper wheel motor 123 to operate according to the received current of the extrusion upper wheel motor 123 using a Proportional Integral Derivative (PID) control method; the main control module 11 is also configured to output a PWM signal with a required duty ratio to the lower wheel motor module 13 to drive the extrusion lower wheel motor 133 to operate according to the received current of the extrusion lower wheel motor 133 using a PID control method.

[0058] The main control module 11 is also configured to determine whether the extrusion upper wheel motor 123 has started or accelerated to the target speed of the upper wheel motor according to the received speed of the extrusion upper wheel motor 123, and to determine whether the extrusion lower wheel motor 133 has started or accelerated to the target speed of the lower wheel motor according to the received speed of the extrusion lower wheel motor 133, and then to adjust the PWM signal output to the upper wheel motor module 12 and the lower wheel motor module 13 according to the determination result.

[0059] In some embodiments, the upper wheel motor target speed is a preset speed value that the upper ball squeezing wheel motor 123 needs to reach in a stable working state, and the lower wheel motor target speed is a preset speed value that the lower ball squeezing wheel motor 133 needs to reach in a stable working state; the upper wheel motor target speed and the lower wheel motor target speed can be set the same or different, and when they are set differently, a speed difference can be formed to control the rotation of the ball. The upper wheel motor target speed and the lower wheel motor target speed can be automatically configured by the main control module 11 according to a preset serving mode (such as flat hitting, topspin, backspin, etc.), or adjusted by the user through a human-computer interaction interface.

[0060] Exemplarily, the main control module 11 can adopt a single-chip microcomputer or a similar controller with analog-to-digital conversion and multiple timer peripherals.

[0061] The tennis ball serving machine ball squeezing wheel control system provided by the embodiments of the present application can realize accurate control of the upper ball squeezing wheel motor 123 and the lower ball squeezing wheel motor 133 by integrating the main control module 11, the upper wheel motor module 12, and the lower wheel motor module 13, and adopting a PID control mode.

[0062] The tennis ball serving machine ball squeezing wheel control system provided by the embodiments of the present application directly sends a full-duty PWM signal in the starting stage to prompt the upper ball squeezing wheel motor 123 and the lower ball squeezing wheel motor 133 to quickly reach a working state, significantly shortening the time required from static to target speed. The PID control mode can adjust the output signal according to real-time feedback, effectively managing the subsequent acceleration process even after the initial full-power start, and ensuring smooth transition to the target speed.

[0063] The tennis ball serving machine ball squeezing wheel control system provided by the embodiments of the present application can realize accurate control of the motor speed by dynamically adjusting the duty cycle of the PWM signal through real-time monitoring of the current and speed of the upper ball squeezing wheel motor 123 and the lower ball squeezing wheel motor 133, and through the PID control mode. This closed-loop control system can automatically correct the output according to the actual running condition of the tennis ball serving machine ball squeezing wheel, thereby ensuring the consistency and accuracy of the serving speed of the tennis ball serving machine.

[0064] When different speeds need to be switched, for example, from 20 km / h to 100 km / h, the PID control mode can quickly respond and adjust the PWM signal, so that the upper ball squeezing wheel motor 123 and the lower ball squeezing wheel motor 133 can reach the new speed in a short time, thereby improving the response speed and flexibility of the system.

[0065] The tennis ball serving machine ball squeezing wheel control system provided by the present application not only solves the problems of slow start, slow response, and slow switching in the related art, but also provides a more efficient and stable serving solution for users through accurate speed control and optimized energy consumption management.

[0066] In some embodiments, the upper wheel motor module 12 includes a first auxiliary control module 121, a first brake module 122, a ball squeezing upper wheel motor 123, an upper wheel current detection module 124, and an upper wheel speed encoder 125. The first auxiliary control module 121 is connected to the main control module 11 and configured to receive the PWM signal sent by the main control module 11. The first auxiliary control module 121 is connected to the first brake module 122 and the ball squeezing upper wheel motor 123, and configured to control the operation of the ball squeezing upper wheel motor 123 and control the deceleration braking of the ball squeezing upper wheel motor 123 through the first brake module 122. The upper wheel current detection module 124 is configured to detect the operating current of the ball squeezing upper wheel motor 123 and send it to the main control module 11. The upper wheel speed encoder 125 is configured to detect the speed of the ball squeezing upper wheel motor 123 and send it to the main control module 11.

[0067] The lower wheel motor module 13 includes a second auxiliary control module 131, a second brake module 132, a ball squeezing lower wheel motor 133, a lower wheel current detection module 134, and a lower wheel speed encoder 135. The second auxiliary control module 131 is connected to the main control module 11 and configured to receive the PWM signal sent by the main control module 11. The second auxiliary control module 131 is connected to the second brake module 132 and the ball squeezing lower wheel motor 133, and configured to control the operation of the ball squeezing lower wheel motor 133 and control the deceleration braking of the ball squeezing lower wheel motor 133 through the second brake module 132. The lower wheel current detection module 134 is configured to detect the operating current of the ball squeezing lower wheel motor 133 and send it to the main control module 11. The lower wheel speed encoder 135 is configured to detect the speed of the ball squeezing lower wheel motor 133 and send it to the main control module 11.

[0068] The first auxiliary control module 121 and the second auxiliary control module 131 both receive the PWM signal from the main control module 11, which can achieve fine adjustment of the speed of the ball squeezing upper wheel motor 123 and the ball squeezing lower wheel motor 133. By changing the duty cycle of the PWM signal, the speed and torque output of the ball squeezing upper wheel motor 123 and the ball squeezing lower wheel motor 133 can be effectively adjusted to meet the needs of different working conditions.

[0069] The first brake module 122 and the second brake module 132 can quickly cut off the power supply of the motor or implement reverse electromagnetic braking when necessary, which can effectively slow down or stop the operation of the ball squeezing upper wheel motor 123 and the ball squeezing lower wheel motor 133, and improve the safety and responsiveness of the system in emergency situations.

[0070] The upper wheel current detection module 124 continuously detects the working state of the upper ball squeezing wheel motor 123, and the lower wheel current detection module 134 continuously detects the working state of the lower ball squeezing wheel motor 133, and feeds back data to the main control module 11. This real-time information transmission mechanism enables the control system to discover abnormal conditions (such as overload) in a timely manner and take appropriate measures to avoid potential failures and prolong the service life of the upper ball squeezing wheel motor 123 and the lower ball squeezing wheel motor 133.

[0071] By using the rotation speed information collected by the upper wheel speed encoder 125 and the lower wheel speed encoder 135, combined with the current detection results, the actual operating conditions of the motors can be more accurately analyzed, providing a basis for control optimization of the main control module 11.

[0072] In this embodiment, the entire upper motor module 12 and lower motor module 13 integrate multiple functions such as control, execution, and sensing into one, reducing the number of external connection cables, reducing system complexity, and also facilitating the miniaturization design level of the overall device.

[0073] In some embodiments, the first auxiliary control module 121 and the second auxiliary control module 131 can be implemented using H half-bridge circuits, the first brake module 122 and the second brake module 132 can be implemented using brake circuits, and the upper wheel current detection module 124 and the lower wheel current detection module 134 can be implemented using sampling and amplification circuits. The motor power supply, H half-bridge circuit, brake circuit, and sampling and amplification circuit can form a specific control and brake circuit. This circuit is different from the H-bridge control circuit in the related art, and it integrates half-bridge control and motor brake circuits together to achieve control functions in the simplest way.

[0074] As shown in FIG. 2, the H half-bridge circuit includes a first field effect transistor MOS1 and a second field effect transistor MOS2. The gate of the first field effect transistor MOS1 is connected to the first input / output port (IO port) PWM_H of the main control module 11, the drain of the first field effect transistor MOS1 is connected to the positive electrode of the motor power supply, the negative electrode of the motor power supply is grounded, and the source of the first field effect transistor MOS1 is connected to the first end of the upper ball squeezing wheel motor 123 and the drain of the second field effect transistor MOS2. The gate of the second field effect transistor MOS2 is connected to the second IO port PWM_L of the main control module 11, and the source of the second field effect transistor MOS2 is connected to the second end of the upper ball squeezing wheel motor 123.

[0075] The brake circuit includes a third field effect transistor MOS3 and a brake resistor R1. The gate of the third field effect transistor MOS3 is connected to the third IO port SW1 of the main control module 11, the drain of the third field effect transistor MOS3 is connected to the source of the first field effect transistor MOS1 through the brake resistor R1, and the source of the third field effect transistor MOS3 is grounded.

[0076] The sampling amplification circuit comprises a sampling resistor R2 and a current amplifier AMP1, a first end of the sampling resistor R2 is connected with the source of the second field effect tube MOS2, and a second end of the sampling resistor R2 is grounded; two input ports of the current amplifier AMP1 are connected with two ends of the sampling resistor R2 respectively, and an output port of the current amplifier AMP1 is connected with the fourth IO port ADC1 of the main control module 11.

[0077] The working process of the above-mentioned control braking circuit comprises a motor acceleration and running process and a motor braking process. In the motor acceleration and running process, the PWM signal with the required duty ratio output by the main control module 11 controls the opening and closing of the first field effect tube MOS1 and the second field effect tube MOS2. The working process is as follows: when the duty ratio is 100%, the first IO port PWM_H of the main control module 11 is at high level, the first field effect tube MOS1 is always open, the second IO port PWM_L of the main control module 11 is at low level, the second field effect tube MOS2 is always closed, and the ball squeezing upper wheel motor 123 is directly powered by the power supply to accelerate or run. When the duty ratio is 50%, in the whole PWM control period, for example, the frequency of the PWM signal is 10 kHz, i.e. the period is 100 microseconds (us), then the half period is 50us. In this 50us period, the first IO port PWM_H of the main control module 11 is at high level, the first field effect tube MOS1 is in the open state, the second IO port PWM_L of the main control module 11 is at low level, the second field effect tube MOS2 is in the off state, and the ball squeezing upper wheel motor 123 absorbs current from the power supply; in the other 50us period, the first IO port PWM_H of the main control module 11 is at low level, the first field effect tube MOS1 is in the off state, the second IO port PWM_L of the main control module 11 is at high level, the second field effect tube MOS2 is in the open state, and the ball squeezing upper wheel motor 123 itself flows through the second field effect tube MOS2. In the acceleration and running process, the third IO port SW1 of the main control module 11 is always at low level, and the third field effect tube MOS3 is always in the off state.

[0078] In the motor braking process, the first IO port PWM_H and the second IO port PWM_L of the main control module 11 are both at low level, the first field effect tube MOS1 and the second field effect tube MOS2 are both in the off state, the third IO port SW1 of the main control module 11 is at high level, the third field effect tube MOS3 is in the open state, and the ball squeezing upper wheel motor 123 absorbs the braking energy of the ball squeezing upper wheel motor 123 through the braking resistor R1.

[0079] In the above embodiment, the start-up program, the acceleration program and the deceleration braking program are configured in the master control module 11. Among them, the flow of the start-up program and the acceleration program is the same, and full duty ratio is adopted to start the ball squeezing upper wheel motor 123 and the ball squeezing lower wheel motor 133, which can greatly shorten the start-up time and the acceleration time.

[0080] Full duty ratio is adopted to start the ball squeezing upper wheel motor 123 and the ball squeezing lower wheel motor 133, that is, the power supply voltage is directly loaded to both ends of the motor. Since the moment requirement of the ball squeezing wheel of the tennis ball serving machine is very large, the start-up current of the ball squeezing upper wheel motor 123 and the ball squeezing lower wheel motor 133 is very large, reaching about 20A or even higher. If full duty ratio is always adopted for start-up, the motor current quickly reaches 20A, and therefore the power supply current is required to reach 20A. Limited by the output capability of the battery of the tennis ball serving machine in the related art (generally 5A-10A continuously) and the low cost requirement of components (the cost of high-current components will increase), the application controls the start-up current of the ball squeezing upper wheel motor 123 and the ball squeezing lower wheel motor 133 to be within the maximum output capability of the battery power supply by full duty ratio start-up and real-time adjustment of the duty ratio of the PWM signal according to the detected motor current and the preset current threshold. For example, the preset current threshold is 10A, and when the current exceeds 10A, the duty ratio of the PWM signal will decrease and is no longer full duty ratio; and when the current is less than 10A, the full duty ratio is continued to be loaded to accelerate the motor.

[0081] As shown in FIG. 3, the flow of the start-up program and the acceleration program configured in the master control module 11 is as follows:

[0082] Full duty ratio (i.e. 100% duty ratio) PWM signals are output to the upper wheel motor module 12 and the lower wheel motor module 13 to control the ball squeezing upper wheel motor 123 and the ball squeezing lower wheel motor 133 to start or start to accelerate.

[0083] The running current of the ball squeezing upper wheel motor 123 detected by the upper wheel current detection module 124 and the running current of the ball squeezing lower wheel motor 133 detected by the lower wheel current detection module 134 are received.

[0084] According to the received running current, the PID control mode is adopted to control the running current of the ball squeezing upper wheel motor 123 and the ball squeezing lower wheel motor 133, and the PWM signal with the required duty ratio is output to make the running current maintain at the preset target current. By setting the target current, the required running current can neither exceed the output capability of the battery nor maximize the performance of the ball squeezing upper wheel motor 123 and the ball squeezing lower wheel motor 133. In order to achieve the fastest acceleration, the target current for motor acceleration can be set to the maximum output current capability of the battery power supply. For example, the maximum output current capability of the battery power supply is 10A, and the target current for motor acceleration is set to 10A.

[0085] In some embodiments, the preset current threshold can be set based on the hardware limit of the motor power supply (such as the maximum peak discharge capacity of a lithium battery) to limit the over-limit current impact at the motor starting moment and prevent the power supply or components from being overloaded. The preset target current can be set according to the continuous output capacity of the power supply (such as the continuous discharge current of a lithium battery) and the acceleration efficiency requirement of the motor, as the dynamic target value of the PID closed-loop control, and the corresponding duty ratio PWM signal is output by the main control module 11 to stabilize the motor operating current. Generally, the target current is less than or equal to the current threshold, ensuring that the current does not break the safety boundary under any working condition.

[0086] The PWM signal with the required duty ratio is output to the upper wheel motor module 12 and the lower wheel motor module 13 to control the operation of the ball squeezing upper wheel motor 123 and the ball squeezing lower wheel motor 133 using the PWM signal with the required duty ratio.

[0087] The rotation speed of the ball squeezing upper wheel motor 123 and the ball squeezing lower wheel motor 133 detected by the upper wheel speed encoder 125 and the lower wheel speed encoder 135 is obtained, and it is determined whether the obtained rotation speed reaches the first target rotation speed. If yes, the starting or accelerating program is exited, otherwise, the operating current of the ball squeezing upper wheel motor 123 and the ball squeezing lower wheel motor 133 is re-received, and the above process is repeated until the rotation speed of the ball squeezing upper wheel motor 123 and the ball squeezing lower wheel motor 133 reaches the first target rotation speed.

[0088] In some embodiments, the first target rotation speed is the stable working rotation speed of the ball squeezing upper wheel motor 123 and the ball squeezing lower wheel motor 133 in the serving mode, and the first target rotation speed can be stored in the parameter register of the main control module 11 and dynamically adjusted through the human-computer interaction interface.

[0089] As shown in FIG. 4, the flow of the deceleration braking program configured in the main control module 11 is as follows:

[0090] The motor power supply is turned off, the third MOS transistor MOS3 is controlled to be turned on, and the motor current is braked through the braking resistor R1 and the third MOS transistor MOS3. Exemplarily, different braking effects can be achieved by selecting different models of braking resistors R1. The selection of the braking resistor R1 depends on the braking current and the braking time, and the braking current determines the braking time. The shorter the required time, the higher the requirement for the braking current. The calculation formula of the braking resistor R1 is: braking resistor R1 = motor back electromotive force / braking current.

[0091] The rotation speeds of the ball squeezing upper motor 123 and the ball squeezing lower motor 133 detected by the upper rotation speed encoder 125 and the lower rotation speed encoder 135 are acquired, and it is determined whether the acquired rotation speeds reach the second target rotation speed, if yes, the deceleration braking program is exited, otherwise, the motor current is adjusted to brake again through the braking resistor R1 and the third field effect tube MOS3, and the above process is repeated until the rotation speeds of the ball squeezing upper motor 123 and the ball squeezing lower motor 133 both reach the second target rotation speed.

[0092] In some embodiments, unless otherwise explicitly stated, “motor” refers to the ball squeezing upper motor 123 and the ball squeezing lower motor 133, which are controlled by the upper motor module 12 and the lower motor module 13 respectively; “motor current” refers to the current of the ball squeezing upper motor 123 and the current of the ball squeezing lower motor 133.

[0093] In some embodiments, the second target rotation speed is a threshold value of the final rotation speed that the ball squeezing upper motor 123 and the ball squeezing lower motor 133 need to reach during the braking process, and the second target rotation speed is smaller than the first target rotation speed; the second target rotation speed can be stored in the parameter register of the main control module 11 and can be dynamically adjusted through the human-computer interaction interface.

[0094] Based on the ball squeezing wheel control system of the tennis ball serving machine provided in the present application, the present application further provides a ball squeezing wheel control method of the tennis ball serving machine, which includes a starting process, an acceleration process and a deceleration braking process, and the starting process and the acceleration process include the following steps:

[0095] S1, the main control module 11 outputs a full duty ratio PWM signal to the upper motor module 12 and the lower motor module 13 to control the ball squeezing upper motor 123 in the upper motor module 12 and the ball squeezing lower motor 133 in the lower motor module 13 to start or start accelerating.

[0096] S2, the upper current detection module 124 detects the running current of the ball squeezing upper motor 123, and the lower current detection module 134 detects the running current of the ball squeezing lower motor 133, and feeds back the detected running current to the main control module 11.

[0097] S3, the main control module 11 outputs a PWM signal with a required duty ratio to the upper motor module 12 and the lower motor module 13 in a PID control mode according to the received running current.

[0098] S4, the first auxiliary control module 121 in the upper motor module 12 and the second auxiliary control module 131 in the lower motor module 13 control the running of the ball squeezing upper motor 123 and the ball squeezing lower motor 133 according to the received PWM signal with the required duty ratio.

[0099] S5, the upper wheel speed encoder 125 detects the rotation speed of the upper ball squeezing wheel motor 123, and the lower wheel speed encoder 135 detects the rotation speed of the lower ball squeezing wheel motor 133, and feeds back the detected rotation speed to the main control module 11.

[0100] S6, the main control module 11 compares the obtained rotation speed with the preset first target rotation speed, if the obtained rotation speed reaches the first target rotation speed, the starting or accelerating program is exited, otherwise, returns to step S3, and repeats steps S3-S6 until the rotation speeds of the upper ball squeezing wheel motor 123 and the lower ball squeezing wheel motor 133 reach the first target rotation speed.

[0101] The deceleration braking process comprises the following steps:

[0102] S7, the main control module 11 controls the opening of the first brake module 122 and the second brake module 132 through the first auxiliary control module 121 and the second auxiliary control module 131 respectively, so as to brake the upper ball squeezing wheel motor 123 and the lower ball squeezing wheel motor 133.

[0103] S8, the upper wheel speed encoder 125 detects the rotation speed of the upper ball squeezing wheel motor 123, and the lower wheel speed encoder 135 detects the rotation speed of the lower ball squeezing wheel motor 133, and feeds back the detected rotation speed to the main control module 11.

[0104] S9, the main control module 11 compares the obtained rotation speed with the preset second target rotation speed, if the obtained rotation speed reaches the second target rotation speed, the deceleration braking program is exited, otherwise, returns to step S7, and repeats steps S7-S9 until the rotation speeds of the upper ball squeezing wheel motor 123 and the lower ball squeezing wheel motor 133 reach the second target rotation speed.

[0105] The tennis ball serving machine ball squeezing wheel control system and control method provided by the application can accelerate the starting time of the tennis ball serving machine ball squeezing wheel, and finally realize the starting or accelerating time of 1-2 seconds, can accelerate the speed switching time of the tennis ball serving machine ball squeezing wheel, and finally realize the speed switching time of 1-2 seconds.

[0106] The embodiments of the present application can be embodied in various hardware, software codes, or a combination of both. For example, an embodiment of the present application can also be a program code containing one or more instructions that can be executed by a data signal processor. The present application can also relate to a computer processor, a digital signal processor, a microprocessor, or a field programmable gate array that executes a process defined by a machine-readable software code or firmware code stored in a storage medium. The processes described can be performed by a single processor or by a combination of processors. Software codes or firmware codes can be developed in different programming languages and different formats to implement the processes described in the embodiments of the present application. The software codes can be compiled to different formats and forms. The software codes can be implemented in different platforms and formats. The software codes can be compiled to different platforms and formats. The different platforms and formats are not intended to limit the spirit and scope of the present application.

Claims

1. A tennis ball serving machine squeeze ball wheel control system, comprising a master control module, an upper wheel motor module and a lower wheel motor module connected to the master control module; The master control module is configured to send full duty cycle pulse width modulation (PWM) signals to the upper wheel motor module and the lower wheel motor module to control the squeeze ball upper wheel motor in the upper wheel motor module and the squeeze ball lower wheel motor in the lower wheel motor module to start or accelerate; The upper wheel motor module is configured to detect the current and speed of the squeeze ball upper wheel motor and send them to the master control module, and the lower wheel motor module is configured to detect the current and speed of the squeeze ball lower wheel motor and send them to the master control module; The master control module is configured to output PWM signals with the required duty cycle to the upper wheel motor module according to the received current of the squeeze ball upper wheel motor using proportional-integral-derivative (PID) control mode to drive the squeeze ball upper wheel motor to run, and to output PWM signals with the required duty cycle to the lower wheel motor module according to the received current of the squeeze ball lower wheel motor using PID control mode to drive the squeeze ball lower wheel motor to run; The master control module is further configured to determine whether the squeeze ball upper wheel motor has started or accelerated to the target speed of the upper wheel motor according to the received speed of the squeeze ball upper wheel motor, and to determine whether the squeeze ball lower wheel motor has started or accelerated to the target speed of the lower wheel motor according to the received speed of the squeeze ball lower wheel motor, and to adjust the PWM signals output to the upper wheel motor module and the lower wheel motor module according to the determination results.

2. The tennis ball serving machine squeeze ball wheel control system of claim 1 wherein, The upper wheel motor module comprises a first auxiliary control module, a first brake module, a squeeze ball upper wheel motor, an upper wheel current detection module, and an upper wheel speed encoder; The first auxiliary control module is connected to the master control module and configured to receive the PWM signals sent by the master control module; the first auxiliary control module is connected to the first brake module and the squeeze ball upper wheel motor and configured to control the operation of the squeeze ball upper wheel motor and to control the deceleration and braking of the squeeze ball upper wheel motor through the first brake module; the upper wheel current detection module is configured to detect the operating current of the squeeze ball upper wheel motor and send it to the master control module, and the upper wheel speed encoder is configured to detect the speed of the squeeze ball upper wheel motor and send it to the master control module.

3. The tennis ball serving machine squeeze ball wheel control system of claim 2 wherein, The lower wheel motor module comprises a second auxiliary control module, a second brake module, a squeeze ball lower wheel motor, a lower wheel current detection module, and a lower wheel speed encoder; The second auxiliary control module is connected to the master control module and configured to receive the PWM signals sent by the master control module; the second auxiliary control module is connected to the second brake module and the squeeze ball lower wheel motor and configured to control the operation of the squeeze ball lower wheel motor and to control the deceleration and braking of the squeeze ball lower wheel motor through the second brake module; the lower wheel current detection module is configured to detect the operating current of the squeeze ball lower wheel motor and send it to the master control module, and the lower wheel speed encoder is configured to detect the speed of the squeeze ball lower wheel motor and send it to the master control module.

4. The tennis ball serving machine squeeze ball wheel control system of claim 2 wherein, The first auxiliary control module is realized by an H half-bridge circuit, the first brake module is realized by a brake circuit, and the upper wheel current detection module is realized by a sampling and amplification circuit.

5. The tennis ball serving machine squeeze ball wheel control system of claim 4 wherein, The H half-bridge circuit comprises a first field effect transistor and a second field effect transistor, the gate of the first field effect transistor is connected with a first IO port of the main control module, the drain of the first field effect transistor is connected with a positive pole of a motor power supply, a negative pole of the motor power supply is grounded, and the source of the first field effect transistor is connected with a first end of a ball squeezing upper wheel motor and a drain of the second field effect transistor; the gate of the second field effect transistor is connected with a second IO port of the main control module, and the source of the second field effect transistor is connected with a second end of the ball squeezing upper wheel motor.

6. The tennis ball serving machine squeeze ball wheel control system of claim 5 wherein, The brake circuit comprises a third field effect transistor and a brake resistor, the gate of the third field effect transistor is connected with a third IO port of the main control module, the drain of the third field effect transistor is connected with the source of the first field effect transistor through the brake resistor, and the source of the third field effect transistor is grounded.

7. The tennis ball serving machine squeeze ball wheel control system of claim 5 wherein, The sampling and amplification circuit comprises a sampling resistor and a current amplifier, a first end of the sampling resistor is connected with the source of the second field effect transistor, and a second end of the sampling resistor is grounded; two input ports of the current amplifier are respectively connected with two ends of the sampling resistor, and an output port of the current amplifier is connected with a fourth IO port of the main control module.

8. The tennis ball serving machine squeeze ball wheel control system of claim 3 wherein, The main control module is configured with a starting program and an acceleration program, and the starting program and the acceleration program are: outputting full-duty-cycle pulse width modulation (PWM) signals to the upper wheel motor module and the lower wheel motor module to control the ball squeezing upper wheel motor and the ball squeezing lower wheel motor to start or start accelerating; receiving running currents of the ball squeezing upper wheel motor detected by the upper wheel current detection module and running currents of the ball squeezing lower wheel motor detected by the lower wheel current detection module; controlling the running currents of the ball squeezing upper wheel motor and the ball squeezing lower wheel motor by a PID control mode according to the received running currents, outputting PWM signals with required duty cycles, and making the running currents keep at preset target currents; outputting the PWM signals with the required duty cycles to the upper wheel motor module and the lower wheel motor module to control the running of the ball squeezing upper wheel motor and the ball squeezing lower wheel motor by the PWM signals with the required duty cycles; acquiring rotation speeds of the ball squeezing upper wheel motor and the ball squeezing lower wheel motor detected by the upper wheel speed encoder and the lower wheel speed encoder, and exiting the starting program or the acceleration program in response to judging that the acquired rotation speeds reach a first target rotation speed.

9. The tennis ball serving machine squeeze ball wheel control system of claim 3 wherein, The main control module is configured with a deceleration braking program, and the deceleration braking program is: turning off the motor power supply, controlling to turn on the first brake module and the second brake module, and braking currents of the ball squeezing upper wheel motor and the ball squeezing lower wheel motor by the first brake module and the second brake module respectively. Obtaining the rotation speed of the ball squeezing upper motor and the ball squeezing lower motor detected by the upper wheel speed encoder and the lower wheel speed encoder, and in response to judging that the obtained rotation speed reaches the second target rotation speed, exiting the deceleration braking program.

10. A tennis ball server ball squeezing wheel control method based on the tennis ball server ball squeezing wheel control system of any one of claims 1-9, the method comprising a starting process, an acceleration process, and a deceleration braking process. The starting process and the acceleration process comprise: The master control module outputs full duty cycle PWM signals to the upper motor module and the lower motor module to control the ball squeezing upper motor in the upper motor module and the ball squeezing lower motor in the lower motor module to start or start accelerating; The upper current detection module detects the operating current of the ball squeezing upper motor, and the lower current detection module detects the operating current of the ball squeezing lower motor, and feeds back the detected operating current to the master control module; The master control module outputs PWM signals with the required duty cycle to the upper motor module and the lower motor module according to the received operating current in a PID control mode; The first auxiliary control module in the upper motor module and the second auxiliary control module in the lower motor module control the operation of the ball squeezing upper motor and the ball squeezing lower motor according to the received PWM signals with the required duty cycle; The upper wheel speed encoder in the upper motor module detects the rotation speed of the ball squeezing upper motor, and the lower wheel speed encoder in the lower motor module detects the rotation speed of the ball squeezing lower motor, and feeds back the detected rotation speed to the master control module; The master control module compares the obtained rotation speed with a preset first target rotation speed, and in response to the obtained rotation speed reaching the first target rotation speed, exits the starting or acceleration program; The deceleration braking process comprises: The master control module controls the opening of the first braking module in the upper motor module and the second braking module in the lower motor module through the first auxiliary control module and the second auxiliary control module, respectively, to brake the ball squeezing upper motor and the ball squeezing lower motor; The upper wheel speed encoder detects the rotation speed of the ball squeezing upper motor, and the lower wheel speed encoder detects the rotation speed of the ball squeezing lower motor, and feeds back the detected rotation speed to the master control module; The master control module compares the obtained rotation speed with a preset second target rotation speed, and in response to the obtained rotation speed reaching the second target rotation speed, exits the deceleration braking program.

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