Motor system with encoder unit arranged at end part and garden vehicle comprising motor system

Abstract

The utility model discloses a motor system with an encoder arranged at the end portion. The motor system comprises a motor unit, a brake unit, an encoder unit and a magnetic unit. The motor unit is provided with a central part, the central part of the motor unit is provided with an output rotating shaft, the output rotating shaft is provided with a first end and a second end, the first end is connected with an external transmission structure, the second end is connected with the magnetic unit, and the brake unit is arranged between the motor unit and the second end. The brake unit is connected to an end cover of the motor unit, the encoder unit is connected to the side, away from the motor unit, of the brake unit, when the output rotating shaft rotates, the magnetic unit is driven to coaxially rotate along with the output rotating shaft, and the encoder unit obtains signals transmitted by the magnetic unit.

Description

Technical Field

[0001] The utility model relates to the field of motor brakes, in particular to a motor system with an encoder unit arranged at the end thereof and a garden vehicle comprising the motor system. Background Art

[0002] The motor is an electromagnetic device that realizes the conversion or transmission of electric energy according to the law of electromagnetic induction. It consists of a stator, a rotor (armature), a housing, bearings and other components. According to the type of working power supply, the motor can be divided into a DC motor and an AC motor. The difference between the two is that the DC motor introduces current into the rotor armature through a Hall sensor or a brush and a commutator, so that the rotor is forced and rotates in the stator magnetic field. The AC motor (taking the AC asynchronous motor as an example) inputs AC power into the stator winding to generate a rotating magnetic field, induces an induced current in the rotor winding, and thus causes the rotor to rotate under force in the stator magnetic field. In order to accurately detect the position and speed of the motor shaft, the DC brushless motors currently on the market are also equipped with encoder units and brake devices, including electromagnetic brakes for controlling the blades to stop, speed generators for collecting motor speed signals, and absolute encoder units for measuring blade position and angle signals. The drive system of this DC brushless motor includes a main control chip, an IGBT module connected to it, and an absolute encoder unit. The encoder unit is essentially a sensor that is used to record the position and speed information of the motor and is a feedback sensing unit. Without the encoder unit, the position and speed of the motor cannot be known. Without the encoder unit, the motor cannot be used, let alone the so-called precise control. It can be said that the encoder unit is a key component, core component, and soul in the motor system, especially when achieving high-precision position movement. The so-called three-ring control of the motor is just a cloud, which cannot be realized and cannot be operated. The accuracy of the encoder unit directly determines the control accuracy and the control effect that can be achieved. The grating encoding structure currently on the market is complex, and an additional laser is required as a light source to capture the grating, which is greatly affected by the environment.

[0003] In addition, most traditional brakes are power-off brakes, which are characterized by the electromagnet losing its magnetic force when the power is off, and the torque spring presses the rotor to provide greater friction to prevent the rotor from rotating, thereby achieving a braking effect. However, since the braking process is greatly affected by the torque spring, affected by factors such as spring fatigue and inability to adjust, it is easy to cause the brake torque to seriously decline, and the torque size cannot be adjusted according to actual needs. In addition, the instantaneous power failure during braking causes an instantaneous impact under the action of the large spring force, and often produces abnormal noises. If the electromagnetic brake fails unexpectedly and there is no emergency plan, the operator will be put in danger.

[0004] In summary, the main disadvantages of traditional power-off electromagnetic brakes are summarized as follows:

[0005] 1. During the vehicle deceleration process, the braking torque cannot be adjusted.

[0006] 2. There is an obvious impact noise at the beginning of braking.

[0007] 3. It is not sensitive to speed control and cannot achieve slow braking.

[0008] 4. The friction states on both sides of the friction plate are inconsistent, resulting in poor braking force stability.

[0009] 5. The torque spring is used many times, which easily leads to fatigue failure of the brake.

[0010] 6. The output torque drops severely and is difficult to effectively adjust.

[0011] 7. The brake is installed inside the housing, resulting in a larger axial dimension of the housing and higher cost.

[0012] 8. The brake structure design is relatively complex, requiring a variety of components, occupying a large installation space, resulting in high cost and inconvenient installation.

[0013] 9. Due to structural limitations, it is impossible to find a stable encoder unit that does not interfere with other structures. Summary of the Utility Model

[0014] The purpose of the present utility model is to solve the above-mentioned requirements, and provide a motor system with an encoder unit arranged at the end that meets the installation position of the encoder unit. Its structure is compact, the encoder unit is also designed to be flat, and at the same time, the axial dimension of the housing is controlled within a small range, and the safety performance also exceeds that of similar products.

[0015] The advantage of the present utility model lies in providing a motor system with an encoder unit arranged at the end, wherein the encoder unit is connected to the side of the brake unit far away from the motor unit, which is convenient for replacing and installing the encoder unit.

[0016] The advantage of the present utility model lies in providing a motor system with an encoder unit arranged at the end, wherein the magnetic unit has at least two polarities. Thus, in the case of one rotation of the magnetic unit, a complete cycle of magnetic field signals can be provided.

[0017] The advantage of the present utility model lies in providing a motor system with an encoder unit arranged at the end, wherein the motor unit is a permanent magnet brushless motor, reducing mechanical wear, and the permanent magnet brushless motor greatly extends the service life of the entire motor system.

[0018] The advantage of the present utility model lies in providing a motor system with an encoder unit disposed at the end. The encoder unit includes a magnetic detection element that outputs a sinusoidal detection signal. Specifically, during the operation of the motor, the position of the magnetic detection element is fixed, and the magnetic unit rotates and changes. Compared with the coaxial rotating encoder unit, the encoder unit of the present utility model has a fixed position and does not need to rotate, so the failure rate and error rate are greatly reduced, and the resolution and accuracy of the encoder unit are also higher than those of products on the market.

[0019] The advantage of the present utility model lies in providing a motor system with an encoder unit disposed at the end. Another manual brake structure is provided outside the brake unit. After the manual brake structure is reciprocally toggled by an external force, it acts on the movable part of the electromagnetic brake structure and replaces the movable part to make the output rotating shaft in two states of braking and releasing braking. In the normal operation state of the motor system, electromagnetic braking can be preferentially adopted. When a fault occurs during the operation of the motor system, manual braking can be urgently adopted. The combined use of manual braking and electromagnetic braking increases the safety and reliability of the motor system and improves the safety factor of the operator.

[0020] The advantage of the present utility model lies in providing a motor system with an encoder unit disposed at the end. The magnetic unit is a bipolar magnet, including a circular bipolar magnetization surface that is bipolar magnetized along the circumferential direction of the output rotating shaft, which simplifies the structure of the magnetic unit and improves the stability of the motor system.

[0021] The advantage of the present utility model lies in providing a garden vehicle with a zero-turn drive gearbox. The zero-turn gearbox includes two sets of the above-mentioned motor systems with an encoder unit disposed at the end. Each motor system controls one wheel part in the traveling assembly. By controlling the forward and reverse rotation of the two sets of motor systems, zero-turn of the traveling assembly is achieved. In this way, in a complex and limited terrain environment, the garden vehicle can move freely, turn flexibly and conveniently, and there is no operation dead angle.

[0022] The present utility model further provides a motor system with an encoder disposed at the end, including: a motor unit having a central part; a brake unit; an encoder unit; a magnetic unit; an output rotating shaft is configured at the central part of the motor unit. The output rotating shaft has a first end and a second end. The first end is connected to an external transmission structure, and the second end is connected to the magnetic unit. The brake unit is disposed between the second ends of the motor unit. The brake unit is connected to the end cover of the motor unit. The encoder unit is connected to the side of the brake unit far from the motor unit. When the output rotating shaft rotates, it drives the magnetic unit to rotate coaxially with the output rotating shaft, and the encoder unit obtains the signal transmitted by the magnetic unit.

[0023] According to an embodiment of the present utility model, the magnetic unit has at least two polarities, and each polarity is evenly wound around the output rotating shaft, and the magnetic unit is adhesively bonded to the second end of the output rotating shaft.

[0024] According to an embodiment of the present utility model, the motor unit is a permanent magnet brushless motor.

[0025] According to an embodiment of the present utility model, the encoder unit includes a magnetic detection element that outputs a sinusoidal detection signal. The motor system further includes a control unit, the control unit is electrically connected to the encoder unit, the control unit is electrically connected to the motor unit, the control unit obtains the operating state of the motor unit through the feedback signal provided by the encoder unit, and finally controls the motor unit.

[0026] According to an embodiment of the present utility model, the brake unit includes an electromagnetic brake assembly. By turning on and off the electromagnetic circuit of the electromagnetic brake assembly, the brake unit and the output rotating shaft can be in two states of braking and releasing braking.

[0027] According to an embodiment of the present utility model, the brake unit includes a manual brake assembly. When the brake unit is reciprocally toggled by an external force, the brake unit and the output rotating shaft are in two states of braking and releasing braking.

[0028] According to an embodiment of the present utility model, the brake unit is further provided with a manual brake assembly. After the manual brake assembly is reciprocally toggled by an external force, it acts on and drives the movable part of the electromagnetic brake assembly and replaces the movable part to make the output rotating shaft be in two states of braking and releasing braking.

[0029] According to an embodiment of the present utility model, the motor unit includes a stator part and a rotor part that rotates relative to the stator part. The stator part is fixed inside the housing of the motor unit. The rotor part is arranged inside the stator part. The output rotating shaft passes through the rotor part. The brake unit and the encoder unit are arranged in sequence along the second end. The electromagnetic brake assembly includes an electromagnet part, a brake disc, a brake pad, and an elastic part. The brake pad is fixed on the output rotating shaft and rotates synchronously with the output rotating shaft. The elastic part is arranged between the brake disc and the output rotating shaft. The brake disc is in two states of braking and releasing braking with the brake pad under the action of the electromagnet part. When in the state of releasing braking, the elastic part is in the maximum deformation state and stores elastic potential energy. When in the state of braking, the elastic part releases at least part of the elastic potential energy so that the brake disc and the brake pad are disengaged from friction, thereby realizing braking.

[0030] According to an embodiment of the present utility model, the encoder unit includes a magnetic detection element that outputs a sinusoidal detection signal. The motor system further includes a control unit, which is electrically connected to the encoder unit and the motor unit. The control unit obtains the operating state of the motor unit through the feedback signal provided by the encoder unit and finally controls the motor unit. The middle of the end face of the electromagnetic brake assembly away from the motor unit has a hole, and the encoder unit covers the hole. The encoder unit is connected to the electromagnetic brake assembly by screws.

[0031] According to an embodiment of the present utility model, a garden vehicle with a zero-turn drive transmission includes a frame unit, a traveling unit, a cutting table unit, and a control unit. Among them, the traveling unit, the cutting table unit, and the control unit are all installed on the frame unit. The control unit is used to control the traveling of the traveling unit. The traveling unit includes a zero-turn drive transmission, and the zero-turn transmission includes two sets of motor systems with an encoder unit provided at one end as described above. Each motor system controls the wheel part in the traveling unit. By the forward and reverse rotation of the two sets of motor systems in cooperation, zero-turn of the traveling unit is achieved.

[0032] The above and other features and advantages of the exemplary embodiments of the present utility model will become more obvious from the following detailed description in conjunction with the drawings, and this description and the drawings are only for exemplary purposes and do not limit the scope of the present utility model in any way. Description of the Drawings

[0033] Figure 1 It is a schematic diagram of the position of the motor system in the vehicle body according to the first preferred embodiment of the present utility model.

[0034] Figure 2 It is an overall schematic diagram of the motor system according to the first preferred embodiment of the present utility model.

[0035] Figure 3 It is a cross-sectional view of the motor system according to the first preferred embodiment of the present utility model.

[0036] Figure 4 It is a cross-sectional view of the encoder according to the first preferred embodiment of the present utility model.

[0037] Figure 5 It is a schematic diagram of the brake unit in the braking state according to the first preferred embodiment of the present utility model.

[0038] Figure 6 It is a control schematic diagram according to the first preferred embodiment of the present utility model.

[0039] Figure 7Schematic diagram of a garden vehicle according to the first preferred embodiment of the present utility model. Detailed implementation manners

[0040] The embodiments of the present application will be described in detail below. The examples of the embodiments of the present application are shown in the accompanying drawings. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application and should not be construed as a limitation of the present application.

[0041] Unless otherwise defined, the technical terms or scientific terms used herein shall have the ordinary meanings understood by those of ordinary skill in the technical field to which the present application belongs. In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation of the present application.

[0042] A motor system with an encoder provided at the end, which can be abbreviated as a motor system in this specification, and the two have the same meaning.

[0043] Figure 1 Schematic diagram of the position of the motor system according to the first preferred embodiment of the present utility model on the vehicle body. As Figure 1 shown, the schematic diagram of the position of the motor system (B10), the motor system (B10) is generally located at the Figure 1 dashed line position in. The vehicle body can be any vehicle containing the motor system (B10), such as a lawn mower, a snow sweeper, a harvester, etc. The said motor system (B1) generally includes two groups and is located between two wheels.

[0044] As Figure 2 shown, a motor system B10 with an encoder provided at the end, the main body part is the motor unit (1), the central area thereof is defined as the central part (101), the outermost left extension rod is the output rotating shaft (11) of the motor unit (1), the right side of the motor unit (1) is the brake unit (2), the right side of the brake unit (2) is the encoder unit (4), the leftmost end of the output rotating shaft (11) is defined as the first end (110), the rightmost end of the output rotating shaft (11) is defined as the second end (111), in addition, the magnetic unit (3) is not drawn in Figure 2 the figure.

[0045] Figures 2 - 7As shown in the figure, a motor system B10 with an encoder at the end includes: a motor unit (1) having a central part (101); a brake unit (2); an encoder unit (4); and a magnetic unit (3). An output rotating shaft (11) is configured at the central part (101) of the motor unit (1). The output rotating shaft (11) has a first end (110) and a second end (111). The first end (110) is connected to an external transmission structure, and the second end (111) is connected to the magnetic unit (3). The brake unit (2) is configured between the second end (111) of the motor unit (1). The brake unit (2) is connected to the end cover of the motor unit (1). The encoder unit (4) is connected to the side of the brake unit (2) away from the motor unit (1). When the output rotating shaft (11) rotates, it drives the magnetic unit (3) to rotate coaxially with the output rotating shaft (11), and the encoder unit (4) can obtain the signal transmitted by the magnetic unit (3).

[0046] The magnetic unit (3) has at least two polarities, and each polarity is evenly wound around the output rotating shaft (11). The magnetic unit (3) is adhesively bonded to the second end (111) of the output rotating shaft (11). The magnetic unit (3) in this embodiment is a bipolar magnet, including a circular bipolar magnetization surface magnetized bipolar along the circumferential direction of the output rotating shaft (11). The motor unit (1) is a 62V permanent magnet brushless motor. The brake unit (2) is respectively disconnected and conducted through an electromagnetic circuit. The brake unit (2) and the output rotating shaft (11) are in two states of braking and releasing braking.

[0047] The encoder unit (4) includes a magnetic detection element (31) that outputs a sinusoidal detection signal. The motor system further includes a control unit (5). The control unit (5) is electrically connected to the encoder unit (4), and the control unit (5) is electrically connected to the motor unit (1). The control unit (5) obtains the operating state of the motor unit (1) through the feedback signal provided by the encoder unit (4) and finally controls the motor unit (1).

[0048] Figure 3 It is a cross-sectional view of the motor system according to the first preferred embodiment of the present invention. The magnetic unit (3) is adhered to the second end (111) of the output rotating shaft (11) with industrial glue.

[0049] Figure 4 It is a cross-sectional view of the encoder according to the first preferred embodiment of the present invention. The encoder unit (4) is located outside the brake unit (2).

[0050] Figure 5It is a schematic diagram of the brake unit in the braking state according to the first preferred embodiment of the present utility model. The brake unit (2) includes an electromagnetic brake assembly (21). Through the conduction and disconnection of the electromagnetic circuit of the electromagnetic brake assembly (21), the brake unit (2) and the output rotating shaft (11) can be in two states: braking and releasing braking. As Figure 2 shown, the brake unit (2) is further provided with a manual brake assembly (22). After the manual brake assembly (22) is reciprocally toggled by an external force, it acts on and drives the movable part of the electromagnetic brake assembly (21) and replaces the movable part to make the output rotating shaft (11) in two states: braking and releasing braking.

[0051] As Figure 4 and Figure 5 shown, the motor unit (1) includes a stator part (13) and a rotor part (12) that rotates relative to the stator part (13). The stator part (13) is fixed in the housing of the motor unit (1). The rotor part (12) is arranged inside the stator part (13). The output rotating shaft passes through the rotor part (12). The brake unit (2) and the encoder unit (4) are arranged in sequence along the second end (111). The electromagnetic brake assembly (21) includes an electromagnet part (210), a brake disc (211), brake pads (212), and an elastic part (213). The brake pads (212) are fixed on the output rotating shaft (11) and rotate synchronously with the output rotating shaft (11). The elastic part (213) is disposed between the brake disc (211) and the output rotating shaft (11). The brake disc (211) is in two states: braking and releasing braking with the brake pads (212) under the action of the electromagnet part (210). When in the releasing braking state, the elastic part (213) is in the maximum deformation state and stores elastic potential energy. When in the braking state, the elastic part (213) releases at least part of the elastic potential energy to make the brake disc (211) and the brake pads (212) release friction, thereby achieving braking. Figure 5 What is shown in is the braking state. At this time, the circuit is disconnected, the electromagnetic part (210) is powered off, and the brake disc (211) and the brake pads (212) are in contact with each other. When in the non-braking state, at this time the circuit is conducting, the electromagnetic part (210) is powered on, the brake disc (211) and the brake pads (212) are separated from each other, the output rotating shaft (11) can operate normally, and the elastic part (213) is at the position with the maximum elastic deformation.

[0052] The middle part of the end face of the electromagnetic brake assembly (21) far away from the motor unit (1) has a hole (214), the encoder unit (4) covers the hole (214), and the encoder unit (4) is connected to the electromagnetic brake assembly (21) by screws.

[0053] As Figure 6 shown, the control unit (5) is electrically connected to the motor unit (1) and the encoder unit (4) respectively.

[0054] As Figure 7 shown, a garden vehicle with a zero-turn drive gearbox includes a frame unit (A), a traveling unit (B), a cutting table unit (C), and an operating unit (D). The traveling unit (B), the cutting table unit (C), and the operating unit (D) are all mounted on the frame unit (A). The operating unit (D) is used to control the traveling of the traveling unit (B). The traveling unit (B) includes a zero-turn drive gearbox (B1). The zero-turn drive gearbox (B1) includes two groups of motor systems (B10) with encoder units provided at the ends. Each motor system (B10) controls the wheel part in the traveling unit (B). By using the forward and reverse rotations of the two groups of motor systems (B10) in cooperation, zero-turn of the traveling unit (B) is achieved.

[0055] Although the present invention has been described in the specification and illustrated in the drawings based on reference to various embodiments, those skilled in the art can understand that the above embodiments are only preferred embodiments. Some technical features in the embodiments may not be necessary for solving specific technical problems, so these technical features can be absent or omitted without affecting the solution of the technical problems or the formation of the technical solutions. Moreover, the features, elements, and / or functions of one embodiment can be appropriately combined, joined, or coordinated with the features, elements, and / or functions of one or more other embodiments, unless the combination, joining, or coordination is clearly inoperable.

Claims

1. A motor system with an encoder unit at the end, characterized in that: include: A motor unit (1) having a central portion (101); Braking unit (2); Encoder unit (3); A magnetic unit (4); an output shaft (11) is arranged at the central portion (101) of the motor unit (1), the output shaft (11) having a first end (110) and a second end (111), the first end (110) being connected to an external transmission structure, the second end (111) being connected to the magnetic unit (4), the brake unit (2) being arranged between the second end (111) of the motor unit (1), the brake unit (2) being connected to an end cover of the motor unit (1), the encoder unit (3) being connected to a side of the brake unit (2) away from the motor unit (1), and when the output shaft (11) rotates, the magnetic unit (4) is driven to rotate coaxially with the output shaft (11), and the encoder unit (3) is able to obtain a signal transmitted by the magnetic unit (4).

2. A motor system with an encoder unit disposed at the end as claimed in claim 1, characterized in that: The magnetic unit (4) has at least two polarities, and each polarity is evenly wound around the output shaft (11), and the magnetic unit (4) is glued to the second end of the output shaft (11).

3. The motor system with an encoder unit disposed at the end as claimed in claim 1, characterized in that: The motor unit (1) is a permanent magnet brushless motor.

4. The motor system with an encoder unit disposed at the end as claimed in claim 1, characterized in that: The encoder unit (3) includes a magnetic detection element (31) that outputs a sinusoidal detection signal. The motor system further includes a control unit (5). The control unit (5) is electrically connected to the encoder unit (3). The control unit (5) is electrically connected to the motor unit (1). The control unit (5) obtains the operating state of the motor unit (1) through a feedback signal provided by the encoder unit (3), and finally controls the motor unit (1).

5. The motor system with an encoder unit disposed at the end as claimed in claim 1, characterized in that: The brake unit (2) comprises an electromagnetic brake assembly (21). By turning on and off the electromagnetic circuit of the electromagnetic brake assembly (21), the brake unit (2) and the output shaft (11) can be in two states: braking and releasing the brake.

6. The motor system with an encoder unit disposed at the end as claimed in claim 1, characterized in that: The brake unit (2) comprises a manual brake assembly (22). When the brake unit (2) is reciprocated by an external force, the brake unit (2) and the output shaft (11) are in two states: braking and releasing the brake.

7. The motor system with an encoder unit disposed at the end as claimed in claim 5, characterized in that: The brake unit (2) is further provided with a manual brake assembly (22). When the manual brake assembly (22) is reciprocated by an external force, it acts on and drives the movable part of the electromagnetic brake assembly (21) and replaces the movable part so that the output shaft (11) is in a braking state or a brake release state.

8. The motor system with an encoder unit disposed at the end as claimed in claim 5, characterized in that: The motor unit (1) comprises a stator part (13) and a rotor part (12) that rotates relative to the stator part (13); the stator part (13) is fixed in a housing of the motor unit (1); the rotor part (12) is arranged inside the stator part (13); the output shaft passes through the rotor part (12); the brake unit (2) and the encoder unit (3) are arranged in sequence along the second end (111); the electromagnetic brake assembly (21) comprises an electromagnet part (210), a brake disc (211), a brake pad (212), and an elastic part (213); the brake pad (212) is fixed to the output The elastic part (213) is disposed on the rotating shaft (11) and rotates synchronously with the output rotating shaft (11). The elastic part (213) is arranged between the brake disc (211) and the output rotating shaft (11). Under the action of the electromagnet part (210), the brake disc (211) and the brake pad (212) are in two states: braking and releasing the brake. When in the releasing state, the elastic part (213) is in the maximum deformation state and stores elastic potential energy. When in the braking state, the elastic part (213) releases at least part of the elastic potential energy so that the friction between the brake disc (211) and the brake pad (212) is released, thereby achieving braking.

9. The motor system with an encoder unit disposed at the end as claimed in claim 8, characterized in that: The encoder unit (3) includes a magnetic detection element (31) that outputs a sinusoidal detection signal. The motor system further includes a control unit (5), the control unit (5) is electrically connected to the encoder unit (3), the control unit (5) is electrically connected to the motor unit (1), the control unit (5) obtains the operating state of the motor unit (1) through a feedback signal provided by the encoder unit (3), and ultimately controls the motor unit (1). The electromagnetic brake assembly (21) has a hole (214) in the middle of the end surface away from the motor unit (1), the encoder unit (3) covers the hole (214), and the encoder unit (3) is connected to the electromagnetic brake assembly (21) by screws.

10. A garden vehicle with a zero-turn drive gearbox, characterized in that: It comprises a frame unit (A), a travel unit (B), a header unit (C), and an operating unit (D), wherein the travel unit (B), the header unit (C) and the operating unit (D) are all mounted on the frame unit (A), the operating unit (D) is used to control the travel of the travel unit (B), the travel unit (B) comprises a zero-turn drive gearbox (B1), the zero-turn drive gearbox (B1) comprises two groups of motor systems (B10) with encoder units arranged at the ends as described in any one of claims 1 to 9, each of the motor systems (B10) controls a wheel part in the travel unit (B), and the zero turn of the travel unit (B) is achieved by the forward and reverse rotation of the two groups of motor systems (B10) in coordination.

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