Patent Publication Number: US-2020283162-A1

Title: Motor control system and unmanned aerial vehicle

Description:
This application is a continuation of International Patent Application No. PCT/CN2018/079007 filed on Mar. 14, 2018, which claims priority to Chinese Patent Application No. 201710561100.5 filed on Jul. 11, 2017, both of which are incorporated by reference in their entireties. 
    
    
     BACKGROUND 
     Technical Field 
     The present application relates to the field of unmanned aerial vehicle (UAV) technologies, and in particular, to a motor control system and a UAV having the same. 
     Related Art 
     An unmanned aerial vehicle (UAV) is a type of new concept equipment in rapid development, which has advantages of high flexibility, fast response, pilotless driving and low operation requirements. The UAV can implement functions of real-time video transmission and high-risk area detection by carrying a plurality of types of sensors or camera devices, and is a powerful supplement of satellite remote sensing and traditional aerial remote sensing. Currently, the application range of the UAV has been expanded to three fields: military, scientific research and civil use, and in particular, to the fields such as power communication, meteorology, agriculture, ocean, exploration, photography, disaster prevention and reduction, crop yield estimation, drug and smuggling prevention, border patrol, public security and anti-terrorism. 
     In the process of implementing the present application, inventors found that the prior art has at least the following problems: Currently, a four-rotor UAV generally has an excessive volume of a hardware circuit board and a heavy weight. This is not only conducive to the miniaturization design of the UAV, and restricts the flexibility of the structure design of the UAV, but also affects and limits the endurance of the UAV. 
     SUMMARY 
     To resolve the foregoing technical problem, embodiments of the present application provide a motor control system having a small size, a compact structure and a light weight, and an unmanned aerial vehicle (UAV) having the motor control system. 
     To resolve the foregoing technical problem, the embodiments of the present application provide the following technical solutions. 
     A motor control system includes a control unit, a first inverter electrically connected to the control unit, a second inverter electrically connected to the control unit, a first motor electrically connected to the first inverter and a second motor electrically connected to the second inverter, the first inverter being connected in parallel to the second inverter. 
     The control unit is configured to output a control signal to the first inverter and the second inverter and to respectively control, by using an alternating signal output by the first inverter and the second inverter, a running state of the first motor and the second motor that are electrically connected thereto. 
     In some embodiments, the first inverter includes at least one first power unit electrically connected to the first motor, the control unit is electrically connected to the at least one first power unit, and the control unit outputs the control signal to the at least one first power unit and controls the running state of the first motor by using an alternating signal output by the first power unit. 
     The second inverter includes at least one second power unit electrically connected to the second motor, the control unit is electrically connected to the at least one second power unit, and the control unit outputs the control signal to the at least one second power unit and controls the running state of the second motor by using an alternating signal output by the second power unit. 
     In some embodiments, the first power unit includes a first power subunit, a second power subunit and a third power subunit that are connected in parallel to each other, and the second power unit includes a fourth power subunit, a fifth power subunit and a sixth power subunit that are connected in parallel to each other. 
     In some embodiments, both the first power unit and the second power unit include a drive circuit configured to receive the control signal, a first power element electrically connected to the drive circuit and a second power element electrically connected to the drive circuit, the first power element being connected in series to the second power element. 
     In some embodiments, both the first power element and the second power element are MOS transistors. 
     In some embodiments, the motor control system further includes a first sampling circuit configured to acquire a three-phase voltage of the first motor and a second sampling circuit configured to acquire a three-phase voltage of the second motor, where the first sampling circuit is electrically connected between the first inverter and the first motor, and the second sampling circuit is electrically connected between the second inverter and the second motor. 
     In some embodiments, the first sampling circuit includes a first sampling resistor and a first operational amplifier circuit connected in parallel to the first sampling resistor; and the second sampling circuit includes a second sampling resistor and a second operational amplifier circuit connected in parallel to the second sampling resistor. 
     In some embodiments, the control unit is an MCU. 
     To resolve the foregoing technical problem, the embodiments of the present application further provide the following technical solution. 
     A UAV includes a body, an arm connected to the body and the foregoing motor control system, a first motor and a second motor being disposed on the arm. 
     In some embodiments, the first motor and the second motor are disposed diagonally. 
     Compared with the prior art, the motor control system of the embodiments of the present application includes a first inverter, a second inverter and a control unit. The control unit is electrically connected to the first inverter and the second inverter respectively, the first inverter is electrically connected to the first motor, and the second inverter is electrically connected to the second motor. Two inverters in the motor control system are electrically connected to one control unit, so that the control unit can control running of two motors, thereby reducing the volume of a hardware circuit board having the motor control system and reducing the weight. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       One or more embodiments are described by way of example with reference to the corresponding figures in the accompanying drawings, and the descriptions are not to be construed as limiting the embodiments. Elements in the accompanying drawings that have same reference numerals are represented as similar elements, and unless otherwise particularly stated, the figures in the accompanying drawings are not drawn to scale. 
         FIG. 1  is a simplified schematic diagram of functional modules of a motor control system according to an embodiment of the present application; 
         FIG. 2  is a schematic structural diagram of the motor control system shown in  FIG. 1 ; 
         FIG. 3  is a schematic structural diagram of a control unit in the motor control system shown in  FIG. 2 ; 
         FIG. 4  is a schematic diagram of functional modules of a motor control system applied to an unmanned aerial vehicle (UAV) according to an embodiment of the present application; and 
         FIG. 5  is a schematic structural diagram of a motor control system applied to a UAV according to an embodiment of the present application. 
     
    
    
     DETAILED DESCRIPTION 
     For ease of understanding the present application, the present application is described in further detail below with reference to the accompanying drawings and specific implementations. It should be noted that when an element is described as being “fixed” on another element, the element may be directly on the another element, or one or more intermediate elements may exist therebetween. When an element is described as being “electrically connected” to another element, the element may be directly connected to the another element, or one or more intermediate elements may exist therebetween. A direction or location relationship indicated by the term “on”, “under”, “inner”, “outer”, “bottom”, or the like used in this specification is a direction or location relationship shown based on the accompanying drawings, and is used only for ease of describing the present application and simplifying the description, but is not intended to indicate or imply that a mentioned apparatus or element needs to have a particular direction and is constructed and operated in the particular direction. Therefore, the direction or location relationship cannot be understood as a limitation to the present application. In addition, the terms such as “first”, “second” and “third” are merely intended to describe the objective and shall not be understood as an indication or implication of relative importance. 
     Unless otherwise defined, meanings of all technical and scientific terms used in this specification are the same as meanings usually understood by persons skilled in the technical field to which the present application belongs. The terms used in this specification of the present application are merely intended to describe specific implementations rather than limit the present application. A term “and/or” used in this specification includes any or all combinations of one or more related listed items. 
     In addition, technical features in different implementations of the present application described below may be combined with each other provided that there is no conflict with each other. 
     Referring to  FIG. 1  and  FIG. 2 , the embodiments of the present application provides a motor control system  100 , including a control unit  23 , a first inverter  21  electrically connected to the control unit  23 , a first motor  11  electrically connected to the first inverter  21 , and a second inverter  22  and a second motor  12  electrically connected to the second inverter  22 . The first inverter  21  is connected in parallel to the second inverter  22 . The control unit  23  is configured to output a control signal to the first inverter  21  and the second inverter  22  and to respectively control, by using an alternating signal output by the first inverter  21  and the second inverter  22 , a running state of the first motor  11  and the second motor  12  that are electrically connected thereto. In this embodiment, the control unit  23 , the first inverter  21  and the second inverter  22  are all integrated on the same circuit board  20 . Two inverters (namely, the first inverter  21  and the second inverter  22 ) in the motor control system  100  are electrically connected to one control unit  23 , so that the control unit  23  can control running of two motors (namely, the first motor  11  and the second motor  12 ), thereby reducing the volume of a hardware circuit board having the motor control system and reducing the weight. 
     In this embodiment, the control unit  23  is an MCU. 
     The first inverter  21  includes at least one first power unit  211 ,  212 ,  213  electrically connected to the first motor  11 . The control unit  23  is electrically connected to the at least one first power unit  211 ,  212 ,  213 . The control unit  23  outputs the control signal to the at least one first power unit  211 ,  212 ,  213  and controls the running state of the first motor  11  by using an alternating signal output by the first power unit  211 ,  212 ,  213 . In this embodiment, the first power unit  211 ,  212 ,  213  includes a first power subunit  211 , a second power subunit  212  and a third power subunit  213  that are connected in parallel. The first power subunit  211 , the second power subunit  212  and the third power subunit  213  are all electrically connected to the first motor  11 . The first power subunit  211 , the second power subunit  212  and the third power subunit  213  receive the control signal from the control unit  23 , so as to control the running state of the first motor  11 . 
     The second inverter  22  includes at least one second power unit  221 ,  222 , 223  electrically connected to the second motor  12 . The control unit  23  is electrically connected to the at least one second power unit  221 ,  222 ,  223 . The control unit  23  outputs the control signal to the at least one second power unit  221 ,  222 ,  223  and controls the running state of the first motor  12  by using an alternating signal output by the second power unit  221 ,  222 ,  223 . In this embodiment, the second power unit  221 ,  222 ,  223  includes a fourth power subunit  221 , a fifth power subunit  222  and a sixth power subunit  223  that are connected in parallel. The fourth power subunit  221 , the fifth power subunit  222  and the sixth power subunit  223  are all electrically connected to the second motor  12 . The fourth power subunit  221 , the fifth power subunit  222  and the sixth power subunit  223  receive the control signal from the control unit  23 , so as to control the running state of the second motor  12 . 
     In this embodiment, the first power subunit  211 , the second power subunit  212 , the third power subunit  213 , the fourth power subunit  221 , the fifth power subunit  222  and the sixth power subunit  223  are all include a drive circuit D 1 , a first power element Q 1  and a second power element Q 2 . The drive circuit D 1  is electrically connected to the first power element Q 1  and the second power element Q 2  respectively. This design has advantages: The switching speed of the drive circuit is very fast, the driving capability is strong, and the turn-off speed of two power elements is fast. 
     Generally, a quantity of power units is determined by a quantity of phases of the motor. In this embodiment, both the first motor  11  and the second motor  12  adopted are a three-phase motor. Therefore, both the first inverter  21  and the second inverter  22  include three power units. The three-phase motor has many advantages such as a simple structure, reliable running, a light weight, and low price. In other embodiments, the first motor and the second motor may alternatively be a single-phase motor. Therefore, the first inverter and the second inverter include only one power unit. The single-phase motor has many advantages such as simple wiring, long service life, and quick start. 
     It can be understood that the first inverter  21  and the second inverter  22  as well as the first motor  11  and the second motor  22  may be completely the same in structures and functions, and only for more clearly describing a connection relationship of the two inverters and the two motors, the “first” and “second” are named respectively. 
     It can be understood that in an embodiment of the present application, both the first power element Q 1  and the second power element Q 2  are MOS transistors. In other embodiments, the first power element Q 1  and the second power element Q 2  may also be an insulated gate bipolar transistor (IGBT) or a thyristor. 
     The drive circuit D 1  is provided with a signal receiving end for receiving the control signal sent by the control unit  23 , so as to turn on or turn off the first power element Q 1  or the second power element Q 2 . The first power element Q 1  and the second power element Q 2  are not turned on or turned off at the same time, thereby forming the alternating signal used for controlling the motor. 
     The motor control system  100  further includes a first sampling circuit  24  configured to acquire a three-phase voltage V 1  of the first motor  11  and a second sampling circuit  26  configured to acquire a three-phase voltage V 2  of the second motor  12 . As a preferred embodiment, the first sampling circuit  24  includes a first sampling resistor R 1  and a first operational amplifier circuit connected in parallel to the first sampling resistor. The second sampling circuit  26  includes a second sampling resistor R 2  and a second operational amplifier circuit connected in parallel to the second sampling resistor. The first sampling resistor R 1  is electrically connected to the second power element Q 2  in the first power subunit  211 , the second power subunit  212  and the third power subunit  213  respectively. The second sampling resistor R 2  is electrically connected to the second power element Q 2  in the fourth power subunit  221 , the fifth power subunit  222  and the sixth power subunit  223  respectively. The first sampling circuit  24  and the second sampling circuit  26  may feed back the three-phase voltage V 1  of the first motor  11  and the three-phase voltage V 2  of the second motor  12  that are acquired to the control unit  23 . The control unit  23  may obtain the running state of the first motor  11  and the second motor  12  according to the received three-phase voltage V 1  and the three-phase voltage V 2 . The control unit  23  may alternatively adjust the running state of the first motor  11  and the second motor  12  according to the received three-phase voltage V 1  and the three-phase voltage V 2 , so that the control unit  23  controls the running state of the first motor  11  and the second motor  12  more precisely. In an embodiment of the present application, the control signal is obtained through vector operation by inputting the three-phase voltage V 1  acquired by the first sampling circuit  24 , the three-phase voltage V 2  acquired by the second sampling circuit  26  and a DC-side voltage Vdc of the motor control system to the control unit  23 . In this embodiment, the control signal output by the control unit  23  includes first pulse-width modulation (PWM) signals (PWM 1 _ 0 , PWM 1 _ 1 , PWM 1 _ 2 , PWM 1 _ 3 , PWM 1 _ 4  and PWM 1 _ 5 ) for controlling the first motor  11  and second PWM signals (PWM 2 _ 0 , PWM 2 _ 1 , PWM 2 _ 2 , PWM 2 _ 3 , PWM 2 _ 4  and PWM 2 _ 5 ) used for controlling the second motor  12 . 
     Each power unit is controlled by two PWM waves, and in other possible embodiments, the power unit may alternatively be controlled by one PWM signal. Specifically, the first PWM signals PWM 1 _ 0  and the PWM 1 _ 1  are input to the drive circuit D 1  in the first power subunit  211 , so as to control the turn-on or turn-off of the first power element Q 1  and the second power element Q 2  in the first power subunit  211 . The first PWM signals PWM 1 _ 2  and the PWM 1 _ 3  are input to the drive circuit D 1  in the second power subunit  212 , so as to control the turn-on or turn-off of the first power element Q 1  and the second power element Q 2  in the second power subunit  212 . The first PWM signals PWM 1 _ 4  and the PWM 1 _ 5  are input to the drive circuit D 1  in the third power subunit  213 , so as to control the turn-on or turn-off of the first power element Q 1  and the second power element Q 2  in the third power subunit  213 . 
     The second PWM signals PWM 2 _ 0  and the PWM 2 _ 1  are input to the drive circuit D 1  in the fourth power subunit  221 , so as to control the turn-on or turn-off of the first power element Q 1  and the second power element Q 2  in the fourth power subunit  221 . The second PWM signals PWM 2 _ 2  and the PWM 2 _ 3  are input to the drive circuit D 1  in the fifth power subunit  222 , so as to control the turn-on or turn-off of the first power element Q 1  and the second power element Q 2  in the fifth power subunit  222 . The second PWM signals PWM 2 _ 4  and the PWM 2 _ 5  are input to the drive circuit D 1  in the sixth power subunit  223 , so as to control the turn-on or turn-off of the first power element Q 1  and the second power element Q 2  in the sixth power subunit  223 . 
     The motor control system  100  in the present application may be applied to mobile devices such as a UAV  200 , a remote control vehicle and an unmanned surface vehicle. As an embodiment of the present application, the motor control system  100  is applied to the UAV  200 . The UAV  200  may be a three-rotor, a four-rotor, a six-rotor or an eight-rotor UAV. 
     As shown in  FIG. 4  and  FIG. 5 , the UAV  200  in the present application is a four-rotor UAV. The UAV includes a body  210 , four arms  220  connected to the body  210  and an electronic speed controller  50  disposed on the body  210 . In some implementations, the four arms  220  may be integrally formed with the body  210 . In some other implementations, the four arms  220  and the body  210  may be independent components that are fixed together by screw locking, gluing or the like after being separately manufactured. The first motor  11  and the second motor  12  are disposed on the arm  220 , and the first motor  11  and the second motor  12  are disposed diagonally relative to the body  210  of the UAV  200  (that is, the first motor  11  and the second motor  12  are respectively disposed on two arms  210  that are disposed diagonally). The control unit  23 , the first inverter  21  electrically connected to the control unit  23  and the second inverter  22  electrically connected to the control unit  23  are integrated in one electronic speed controller  50 . It can be understood that other two diagonally disposed motors may also be controlled by adopting the integrated electronic speed controller  50  in the embodiments of the present application. This design has the advantages: When the UAV  200  is in flight, one electronic speed controller  50  is damaged, and the other electronic speed controller  50  can control the motor located diagonally to continue running, so that the UAV  200  can land smoothly. If one electronic speed controller  50  controls two motors located on the same side, and either of the two electronic speed controllers  50  is damaged, the UAV  200  may roll over and crash. Controlling the motor located diagonally by using the same electronic speed controller  50  can help reduce the volume of a circuit board of the electronic speed controller in the UAV, thereby meeting a miniaturization design requirement of the UAV, and improving the endurance of the UAV. 
     Finally, it should be noted that the foregoing embodiments are merely intended for describing the technical solutions of the present application, but not for limiting the present application. Under the idea of the present application, the technical features in the foregoing embodiments or different embodiments may also be combined, the steps may be implemented in any order and there are many other variations of different aspects of the present application, which are not provided in detail for brevity. Although the present application is described in detail with reference to the foregoing embodiments, persons of ordinary skill in the art should understand that they may still make modifications to the technical solutions described in the foregoing embodiments or make equivalent replacements to some technical features thereof, and such modifications or replacements do not cause the essence of corresponding technical solutions to depart from the scope of the technical solutions of the embodiments of the present application.