Patent Publication Number: US-2019173399-A1

Title: Security mechanisms for electric motors and associated systems

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims the benefit of and priority to U.S. Provisional Applications No. 62/593,854, filed Dec. 1, 2017, No. 62/650,895, filed Mar. 30, 2018, and No. 62/650,916, filed Mar. 30, 2018, which are incorporated herein by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     The present technology is directed to security mechanisms and associated systems for electric motors. More particularly, the present technology is directed to a “coil-based” security mechanism or system that can generate a countering torque in response to unauthorized user actions. 
     BACKGROUND 
     It is important to have a security mechanism or system for a vehicle to prevent an unauthorized use. Conventionally, for example, a user can install or put a physical lock (e.g., a bike lock) on a wheel of the vehicle to prevent an unauthorized use. Sometimes, however, installing a conventional lock can be troublesome and inconvenient. For example, a user may need to carry a key to unlock the conventional lock. As another example, sometimes a user&#39;s hands can be full and therefore installing/locking/unlocking the conventional lock can be bothersome. Moreover, attempting to move a vehicle that is locked by a conventional lock may result in permanent damages to the vehicle. Therefore, there is a need for an improved security mechanism or system to address the foregoing issues. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1 a    is a block diagram illustrating a system in accordance with an embodiment of the present technology. 
         FIG. 1 b    is a schematic circuit diagram of a “coil-based” security mechanism or system in accordance with embodiments of the present technology. 
         FIG. 1 c    is a schematic circuit diagram, illustrating drive circuitry in accordance with embodiments of the present technology for converting a direct current (DC) to three-phase alternating currents (AC). 
         FIGS. 1 d -1 i    are schematic circuit diagrams, illustrating three-phase alternating currents (AC) generated by the drive circuitry in various angles. 
         FIGS. 2 a -2 c    illustrate various components of a hub apparatus in accordance with embodiments of the present technology. 
         FIG. 3 a    illustrates a stator assembly in accordance with embodiments of the present technology. 
         FIGS. 3 b  and 3 c    illustrate a coil-based security mechanism or system in accordance with embodiments of the present technology. 
         FIGS. 4 a -4 c    illustrate components of a locking device in accordance with embodiments of the present technology. 
         FIG. 5  illustrates a hub apparatus that is placed in a wheel in accordance with embodiments of the present technology. 
         FIGS. 6-7  are flowcharts illustrating methods in accordance with embodiments of the disclosed technology. 
     
    
    
     The drawings are not necessarily drawn to scale. For example, the dimensions of some of the elements in the figures may be expanded or reduced to help improve the understanding of various embodiments. Similarly, some components and/or operations may be separated into different blocks or combined into a single block for the purposes of discussion of some of the embodiments. Moreover, although specific embodiments have been shown by way of example in the drawings and described in detail below, one skilled in the art will recognize that modifications, equivalents, and alternatives will fall within the scope of the appended claims. 
     DETAILED DESCRIPTION 
     The present technology is directed to a security mechanism or system for an electric motor with multiple sets of coils. In some embodiments, when the electric motor is turned off (or has been turned off for a predetermined time period, such as 5-10 minutes), the security system short-circuits part or all sets of the multiple sets of coils. In this disclosure, “short-circuiting” a coil means generating a closed electrical path between part of all coils in the electric motor. The short-circuited coils can form one or more closed loops. When the surrounding magnetic field changes (e.g., caused by a rotation of a rotor having magnets relative to a stator having the coils, such as an unauthorized user attempting to rotate a wheel driven by the electric motor), an electric current is generated or induced in the short-circuited coils. The induced electric currents formed in the closed loops generate an induced, opposing magnetic field (and heat). The induced magnetic field results in a force that opposes the movement of the rotor. As a result, the induced force/torque can prevent or at least impede (e.g., slow down) the unauthorized action (e.g., rotation). 
     When an unauthorized action creates a greater magnetic field change (e.g., to rotate the motor faster), the present system can respond with a greater induced force/torque to impede or restrain the unauthorized action. For example, when an unauthorized user slowly rotates a wheel driven by the electric motor of the present system, the unauthorized user may still be able to rotate the wheel; however, he/she can “feel” an induced torque, in a direction opposite the moving direction, generated by the present system to “slow” him/her down. When the unauthorized user increases the rotational speed, the induced force/torque can escalate accordingly, which makes the unauthorized rotation more and more difficult. As a result, the “coil-based” or “motor-based” security mechanism or system that can effectively prevent, or at least impede, unauthorized activities of an electric motor having multiple sets of coils. 
     In some embodiments, the present security mechanism or system can be implemented in a system that includes an electric motor. In such embodiments, the present security mechanism can be used to impede an unauthorized rotation of a rotor of the electric motor. For example, the present security mechanism or system can be implemented in a powertrain assembly in a vehicle configured to drive/power the vehicle. In such embodiments, the power train assembly can include a motor having multiple sets of coils and a security unit or security component configured to short-circuit part or all of these coils (so as to activate the security mechanism). In some embodiments, the security unit can include a conductive plate and an actuator configured to move the conductive plate to short-circuit part or all of the coils (and accordingly create closed loops by the short-circuited coils). The vehicle described herein can be one-wheeled, two-wheeled or three wheeled. The vehicle can be a self-balancing electric vehicle such as a Segway. In some embodiments, the vehicle can be an electric hoverboard, an electric bicycle, vehicles based on EPAC (Electrically Power Assisted Cycles) standards, a moped, an electric scooter, an electric motorcycle or the like. The vehicle can also be a 4-wheeled vehicle like an electric car. 
     In some embodiments, the present security mechanism or system can be implemented in a hub apparatus or hub assembly configured to rotate a wheel of a vehicle (e.g., a bicycle, tricycle, etc.). The hub apparatus includes a rotor assembly, a shaft, and a stator assembly. The stator assembly is fixedly coupled to the shaft, and the shaft extends through the rotor assembly. The rotor assembly can be rotated relative to the stator assembly and the shaft. The rotor assembly of the hub apparatus is coupled to the wheel/rim of the vehicle, and the shaft is fixedly coupled to the vehicle (e.g., to a vehicular structure such as a frame). The hub apparatus is configured to rotate the wheel either with or without human power to move (or at least facilitate the movement of) the vehicle. In some embodiments, the electric motor can include magnets in the rotor assembly and coils in a stator assembly. In other embodiments, the magnets can be positioned in the stator assembly, whereas the coils can be positioned in the rotor assembly. In some embodiments, the electric motor can be powered by a battery, a battery assembly, or other suitable energy storage devices. In some embodiments, the hub apparatus as a whole can be considered as an electric motor. The disclosed security mechanism can effectively prevent, or at least impede, an unauthorized rotation of the hub apparatus. 
     In some embodiments, the present technology can be implemented in a vehicle driven by the foregoing hub apparatus. The present technology is also directed to a security, locking and/or braking mechanism that can generate torque or rotational force (e.g., by a change in magnetic fields caused by electric current induced in part or all coils of a stator) to counter an unauthorized action. 
     In some embodiments, the present security, locking, braking mechanism can be used to prevent or impede the rotation of various types of rotating devices (e.g., a rotor, a wheel, a rotating component of an electric motor, etc.). In some embodiments, the security, locking, and/or braking mechanism can be implemented in any apparatus that has suitable coils and circuities. In some embodiments, the security, locking, and/or braking mechanism can be used as a theft-prevention mechanism. 
     The present technology also discloses a (physical) locking device that can cooperate with the foregoing coil-based security mechanism (e.g., to enhance security). The present locking device can be installed in a hub apparatus (or an electric motor) and configured to stop or at least partially restrain/prevent a rotating portion (e.g., a rotor/rotor assembly) of the hub apparatus from rotating relative to a stationary portion (e.g., a stator/stator assembly) of the hub apparatus. In some embodiments, the locking device can include a stopper (e.g., positioned at the stator) configured to contact a corresponding stopping bump (e.g., positioned at the rotor) so as to at least partially prevent the rotation of the rotor. Embodiments of such locking devices are discussed in detail with reference to  FIGS. 4 a   - 4   c.  In some embodiments, the locking device can be implemented in a hub apparatus without the coil-based security mechanism. 
       FIG. 1 a    is a block diagram illustrating a system  900  in accordance with embodiments of the present technology. In some embodiments, the system  900  can be implemented in a vehicle with a wheel driven by an electric motor (e.g., the motor  901  in  FIG. 1 a   ). In some embodiments, the system  900  can be implemented in a powertrain assembly for driving a vehicle (e.g., the motor  901  is configured to drive the wheel via one or more power transmission components such as a belt, chain, gear, etc.). In some embodiments, the system  900  can be implemented in a hub apparatus having a motor therein. In some embodiments, the system  900  can be implemented in any suitable device that includes an electric motor having multiple set of coils. 
     As shown in  FIG. 1   a,  the system  900  includes a motor  901 , an electric control unit (ECU) or controller  902  configured to control the motor  901 , and a power supply  903  configured to power the motor  901 . The motor  901  includes a stator (or stator assembly) and a rotor (or rotor assembly) configured to rotate relative to the stator. The motor  901  includes multiple sets of coils, located either in the stator or the rotor. In the embodiments where the coils are in the stator, the rotor can include multiple magnets configured to rotate relative to the stator. In the embodiments where the magnets are in the stator, the rotor can include multiple coils configured to rotate relative to the rotor. The system  900  further includes a motor control unit (MCU)  904 . The motor control unit  904  include a drive circuitry  905  and a circuit controller  906 . The drive circuitry  905  includes multiple switches configured to supply currents to the motor  901  (e.g., via power lines X, Y, and Z, to be discussed in detail below). The circuit controller  906  is configured to control the switches in the drive circuitry  905  based on the instructions from the ECU  902  or default rules embedded in the circuit controller  906 . In some embodiments, the ECU  902  can further communicate with or controlled by a portable device (e.g., a user&#39;s smartphone or wireless key-fob, etc.) via a wireless communication or via a dashboard disposed on the vehicle with I/O device configured to interact with the user. 
     In the illustrated embodiments, the motor  901  has three sets of coils, each set including a group of serially connected coils positioned 180-degree (or other degrees) apart around the stator. The three sets of coils can be circumferentially arranged or positioned (e.g.,  FIG. 3 a   ) next to one another around the stator such that, when electric currents flow through these coils, the coils generate magnetic fields to rotate multiple magnets in the generated magnetic fields. For example, in the embodiments where the coils are arranged in the stator, the magnets in the rotor can be rotated by the induced magnetic fields generated by the coils. 
     The drive circuitry  905  is configured to provide currents to the coils. The drive circuitry  905  is configured to receive a direct electric current (DC) from the power supply  903  (e.g., a battery, a capacitor, an energy storage device, etc.) and then forms an alternating current (AC) in various phases. In the illustrated embodiments, the drive circuitry  905  is configured to receive a DC voltage and form an alternating current with three phases (e.g., any two of the phases have a 120-degree difference). The three-phase AC can be supplied to the three sets of coils in the motor  901 , respectively. By this arrangement, the three-phase alternating current in the three sets of coils result in a continuous, alternating magnetic field change so as to drive the motor  901  (e.g., by rotating the corresponding magnets). As shown in  FIG. 1   a,  the three-phase alternating current is supplied to the three sets of coils via three-phase power lines X, Y and Z, respectively. 
     The security unit  907  is configured to selectively short the wires of the coils (e.g., to short/connect part or all of the three-phase power lines X, Y and Z, such that corresponding part or all of the three sets of coils can be short-circuited). In one embodiment, the security unit  907  is controlled by the ECU  902 . When part or all of the three-phase power lines X, Y and Z are connected with one another, the corresponding one(s) of the three sets of coils is(are) short-circuited. A short-circuited coil set forms a closed loop. In other words, any induced current in the short-circuited coil does not flow out of the loop. Instead, it flows in the loop and accordingly generates an induced magnetic field. When an unauthorized user attempts to rotate a wheel attached to the rotor of the motor (e.g., by pushing the vehicle to rotate its wheel), the induced magnetic field can form a torque to counter or impede the unauthorized rotation. By this arrangement, the system  900  provides an effective security mechanism to prevent or impede unauthorized actions such as theft. 
     In some embodiments, the security unit  907  can include a conductive plate  111  ( FIG. 1 b   ) and an actuator configured to move the conductive plate  111  to short-circuit the coils (and accordingly create closed loops by the short-circuited coils). In other embodiments, the security unit  907  can include a switch to short-circuit the coils. In some embodiments, the switch can be a physical, mechanical, or electro-mechanical switch. In other embodiments, the switch can be a transistor-based switch such as a metal-oxide-semiconductor-field-effect-transistor (MOSFET) switch. 
     In some embodiments, when the motor  901  is turned off (e.g., power off), the ECU  902  can immediately instruct the security unit  907  to short-circuit the coils in the motor  901 . In other embodiments, the ECU  902  can instruct the security unit  907  to short-circuit the coils in the motor  901  after the motor  901  has been turned off for a predetermined time period (e.g., 5-10 minutes). Yet in some other embodiments, the ECU  902  can instruct the security unit  907  to short-circuit the coils in the motor  901  after the system  900  (i.e., the vehicle) is left “unused” (e.g., the vehicle does not receive a user input or a user instruction to operate) for a predetermined period of time. 
     In some embodiments, after the ECU  902  instructs the security unit  907  to short-circuit the coils in the motor  901 , the ECU  902  can further verify whether these coils are short-circuited. For example, the ECU  902  can (1) inform the circuit controller  906  of the MCU  904  that the coils are to be short-circuited; and (2) instruct the circuit controller  906  to send a testing signal (e.g., a relatively small amount of current, a pulse, a square wave, etc.) to the drive circuitry  905  to see if the coils have been short-circuited. In some embodiments, the circuit controller  906  can send a series of signals (e.g., pulses, waves, etc.) to the drive circuitry  905 , and then to see if the coils have been short-circuited as expected. The testing methods are discussed below in detail with reference to  FIG. 1   b.    
     If the circuit controller  906  confirms that the coils are short-circuited (e.g., the testing signal are reflected as expected), the circuit controller  906  can (1) notify the ECU  902  about the confirmation (e.g., sending a confirmation signal); and (2) enter a hibernation mode (e.g., to preserve energy). After receiving the confirmation from the circuit controller  906 , the ECU  902  can then hibernate (e.g., to preserve energy). 
       FIG. 1 b    is a schematic circuit diagram of a “coil-based” security mechanism in accordance with embodiments of the present technology. As shown in  FIG. 1   b,  “La, Ra”, “Lb, Rb” and “Lc, Rc” represent the equivalent impedances (e.g., combinations of inductances and resistances) of the three coils (or sets of coils) of the motor  901 , respectively (e.g., coils  108   a,    108   b  and  108   c  shown in  FIG. 1 b   ). As shown, the coils  108   a,    108   b  and  108   c  are coupled to the drive circuitry  905 . The drive circuitry  905  is configured to control the coils  108   a,    108   b  and  108   c  by supplying a three-phase alternating current (AC) (e.g., with a 120-degree difference between two phases) thereto. The three-phase AC is converted from a direct current (DC) source such as a battery. Embodiments of the three-phase AC are discussed below with reference to  FIG. 1 c   - 1   i.    
     As shown in  FIG. 1   b,  the connectors  109   a,    109   b  and  109   c  can be coupled to contacting points A, B, and C. By this arrangement, when the conductive plate  111  of the security unit  907  contacts the connectors  109   a,    109   b  and  109   c,  the coils  108   a,    108   b  and  108   c  are short-circuited as described above. 
     In some embodiments, relays  110   a,    110   b,  and  110   c  can be positioned between the connectors  109   a,    109   b  and  109   c  and contacting points A, B, and C, respectively (in  FIG. 1   b,  points A′, B′, and C′ represent contacting points with same voltages as points A, B, and C, respectively). The relays  110   a,    110   b,  and  110   c  can act as a safety fuse to the coils  108   a,    108   b  and  108   c.  For example, if the current in one of the short-circuited coils  108   a,    108   b  and  108   c  exceeds a certain threshold or the temperature of a coil exceeds a limit as measured by a temperature sensor adjacent to coil (not shown), the corresponding one of the relays  110   a,    110   b,  and  110   c  can form an open circuit so as to prevent the short-circuited coils  108   a,    108   b  and  108   c  from over-heating or melting down. In some embodiment, the relays  110   a,    110   b,  and  110   c  can be “recovered,” or be set back to form a closed circuit, (1) after a predetermined amount of time, or (2) in response to detecting that the current in one of the short-circuited coils  108   a,    108   b  and  108   c  is no longer exceeding the threshold. 
     As discussed above, in some embodiments, after the conductive plate  111  short-circuits the coils  108   a,    108   b  and  108   c  (e.g., the conductive plate  111  is moved by an actuator (not shown) to contact the connectors  109   a,    109   b  and  109   c ), the ECU  902  can further verify whether these coils  108   a,    108   b  and  108   c  are short-circuited. For example, referring to both  FIGS. 1 a    and  1   b,  the ECU  902  can (1) send a signal to the circuit controller  906  indicating that the conductive plate  111  has been actuated in order; and (2) instruct the circuit controller  906  to send a testing signal (e.g., a relatively small amount of current, a pulse, a square wave, etc.) to see if the coils  108   a,    108   b  and  108   c  have been short-circuited. For example, the circuit controller  906  can generate a testing wave/pulse/signal/current and send it to the drive circuitry  905  at contacting point A. The circuit controller  906  then measure the signal at contacting points B and/or C. Based on the characteristics (e.g., strength, form, shape, etc.) of the detected signal wave/pulse/current, the circuit controller  906  can determine whether the coils  108   a,    108   b  and  108   c  are short-circuited. For example, if the wave went through part or all of the coils  108   a,    108   b  and  108   c,  the characteristics of the wave would be changed due to the impendence of these coils  108   a,    108   b  and  108   c.  By comparing the original testing signal (at one point, for example, contacting point A) and the detected wave (at another point, for example, contacting point B or C), the circuit controller  906  can determine whether the coils  108   a,    108   b  and  108   c  are short-circuited as expected. In some embodiments, when the original and detected testing signals are substantially similar or generally the same (e.g., strength, wave form, etc.), the system  900  can confirm that the coils are short-circuited as expected. The circuit controller  906  can then transmit a signal indicating the testing result to the ECU  902 . 
     In some embodiments, the testing result can be analyzed in various ways depending on the types of the testing signals and corresponding measuring schemes. For example, in some embodiments where the contacting points A, B and C are short-circuited by the conductive plate  111  and the testing signal is a small amount of current, if the coils are short-circuited as expected, the amount of the current measured/sensed at the contacting point B or C should be similar to the amount of the original testing current applied to the contacting point A. 
     In some embodiments, if the circuit controller  906  cannot confirm that the coils are short-circuited, the circuit controller  906  can notify the ECU  902  about the failure of confirmation. The ECU  902  can then (1) run a test to check if the security unit  907  functions properly, and/or (2) notify a user of the system  900  about the failure of confirmation. In some embodiments, after the ECU  902  notifies the user (e.g., by sending a message to the user&#39;s smartphone or a display disposed on the vehicle where the system  900  is implemented), the ECU  902  can go hibernate (or enter a hibernation or sleep mode). Since the mechanism of short-circuiting the coils of the motor has a relatively simple structure/arrangement (e.g., by using switches and the conductive plate  111 ), the mechanism is reliable. If the controller does not receive the confirmation, it can be caused by malfunction of the motor itself. As a result, the controller (and the circuit controller also) is configured to enter the hibernation mode to prevent further damages caused by a possible malfunction resulting in the failure of confirmation. Similarly, the circuit controller  906  can go hibernate for the same reason after notifying the ECU  902  about the failure of confirmation. 
     In some embodiments, the ECU  902  can determine that the circuit controller  906  may not function properly if the circuit controller  906  cannot confirm that the coils are short-circuited after a predetermined time period (e.g., from the time that the ECU  902  instructs the circuit controller  906  to send a testing signal). In such embodiments, the ECU  902  (and the circuit controller  906 ) can also enter a hibernation mode. 
     In some embodiments, when the ECU  902  determines that the circuit controller  906  fails to confirm the connection status of the coils (e.g., short-circuited or not short-circuited), the ECU  902  can send a notification to a user and then go hibernate. In some embodiments, the ECU  902  can instruct a physical locking device (e.g., locking device  400  discussed below with reference to  FIG. 4 a   ) to lock the system  900  if the confirmation is not successfully received. 
     In some embodiments, when a user turns on the power of the system  900  (e.g., the ECU  902  receives a wireless signal from a key fob or mobile phone, or a signal generated response to pressing a physical button of a hub apparatus (a button to activate the hub apparatus), the ECU  902  instructs the security unit  907  to let the coils of the motor  901  (electrically and physically) couple to the drive circuitry  905  and the power supply  903  (e.g., not short-circuited or closed-circuited). The ECU  902  then instructs the circuit controller  906  to send a testing signal to see if the coils are properly, electrically coupled to the power supply  903  (without being short-circuited). If so, the motor  901  remains turned on and is ready for receiving power from the drive circuitry  905  and the power supply  903 . If not, the circuit controller  906  notifies the ECU  902  about the confirmation that the coils are still short-circuited, and then both the ECU  902  and the circuit controller  906  can go hibernate. In some embodiments, the drive circuitry  905  can include small resistors (not shown) in line with the leads/wires that feed the coils. The circuit controller  906  can detect voltage across the resistors to detect the signals on each lead and therefore determine if the coils are short-circuited. 
     In some embodiments, when the ECU  902  determines that the circuit controller  906  fails to confirm the connection status of the coils (e.g., short-circuited or not short-circuited), the ECU  902  can send a notification to a user and then go hibernate. In some embodiments, the ECU  902  can instruct a physical locking device (e.g., element  400  discussed below with reference to  FIG. 4 a   ) to lock the system  900 . 
     Referring to  FIG. 1 c   , as discussed above, the drive circuitry  905  can convert a direct circuit (DC) into three-phase alternating currents (AC 1 , AC 2 , and AC 3 ). As shown in  FIGS. 1 d   - 1   i,  the three-phase alternating currents AC 1 , AC 2 , and AC 3  can flow through various combinations of the coils  108   a,    108   b  and  108   c,  resulting in changes of magnetic fields, which rotates the rotor of the motor  901 .  FIGS. 1 d -1 i    illustrate how the current flows in the coils in a rotation cycle (360 degrees). 
       FIG. 1 d    shows that alternating current AC 1  starts at the contacting point A, flows through coils  108   a  and  108   b,  and returns to the contacting point B. In this phase, the rotor rotates from 0 to 60 degrees.  FIG. 1 e    shows that alternating current AC 1  starts at the contacting point A, flows through coils  108   a  and  108   c,  and returns to the contacting point C. In this phase, the rotor rotates from 60 to 120 degrees.  FIGS. 1 d  and 1 e    show a first phase of the three-phase AC. 
       FIG. 1 f    shows that alternating current AC 2  starts at the contacting point B, flows through coils  108   b  and  108   c,  and returns to the contacting point C. In this phase, the rotor rotates from 120 to 180 degrees.  FIG. 1 g    shows that alternating current AC 2  starts at the contacting point B, flows through coils  108   b  and  108   a,  and returns to the contacting point A. In this phase, the rotor rotates from 180 to 240 degrees.  FIGS. 1 f  and 1 g    show a second phase of the three-phase AC. 
       FIG. 1 h    shows that alternating current AC 3  starts at the contacting point C, flows through coils  108   c  and  108   a,  and returns to the contacting point A. In this phase, the rotor rotates from 240 to 300 degrees.  FIG. 1 i    shows that alternating current AC 3  starts at the contacting point C, flows through coils  108   c  and  108   b,  and returns to the contacting point B. In this phase, the rotor rotates from 300 to 360 degrees.  FIGS. 1 h  and 1 i    show a third phase of the three-phase AC. 
       FIGS. 2 a -2 c    illustrate various components of a hub apparatus  200  in accordance with embodiments of the present technology. As previously described, the system  900  can be implemented in a hub apparatus that powers a vehicle. As shown in  FIG. 2 a   , a hub apparatus  200  includes a housing  101  and a hub flange (or ring structure)  103  extending from the housing  101  and configured to accommodate multiple spokes  105  (e.g., the other end of the spoke  105  can be coupled to a front/back wheel of a bike). 
     In some embodiments, the housing  101  can be assembled from multiple housing components. In some embodiments, the housing  101  can include a first housing component and a second housing component coupled to each other and together form an inner/interior/internal space to accommodate elements of the hub apparatus  200 . In some embodiments, for example, the housing  101  can include a sidewall  101   a  and an outer rim  101   b  extending around the outer circumference of the sidewall  101   a.  The outer rim  101   b  has a height or a depth that defines the interior space in the housing  101 . 
     As shown in  FIG. 2 a   , the sidewall  101   a  is formed with a side opening at its center, allowing a shaft  209  to pass through. The opening is configured to accommodate a side cover  502  (see e.g.,  FIG. 5 ). The side cover  502  is configured to rotate with the housing  101  relative to the shaft  209 . In some embodiments, a bearing (not shown) can be positioned between the side cover and the shaft  209 , which enables the side cover  502  to rotate relative to the shaft  209 . 
     As best shown in  FIG. 2 b   , fitted into the interior space of the housing  101  are a main circuit board  203 , a battery assembly  205 , and a coil assembly  207  that are fixedly directly or indirectly to an axle or shaft  209  passing through the center of the hub apparatus  200 . In such embodiments, the housing  101  and a number of magnets (not visible in  FIG. 2 a    or  2   b ; see e.g.,  FIG. 2 c   ) on the interior of the housing  101  together form a rotor assembly  222 . Further, the main circuit board  203 , the battery assembly  205 , and the coil assembly  207  together can be considered as the stator assembly  208 . 
     When an electric current provided by the battery pack (e.g., the battery assembly  205 ) passes through coils of the stator assembly  208 , magnetic fields are generated and accordingly move the magnets of the rotor assembly  222  to rotate the rotor assembly  222  about axis R (or shaft  209 ). In some embodiments, the battery pack can be positioned external to the hub apparatus  200 . As a result, the housing  101  and a wheel attached to the housing  101  via the spokes  105  are also rotated to move a scooter, a bicycle, or a vehicle. 
     In the illustrated embodiment, the hub flange or ring structure  103  ( FIG. 2 a   ) and the sidewall  101   a  are concentrically positioned. The hub flange or ring structure  103  is positioned around a center point of the sidewall  101   a.  In other embodiments, the hub flange or ring structure  103  can have different dimensions (e.g., closer to the outer edge of the housing  101  or nearer to the center point). As shown, the hub flange or ring structure  103  includes a plurality of openings  107  configured to receive the ends of the multiple spokes  105 , respectively. 
     Each spoke  105  has an outer end configured to couple to a wheel/rim structure (not visible in  FIG. 2 a   ) and an inner, flared (or spherical) end  211  that seats against a correspondingly shaped recess formed in an interior circumference of the hub flange or ring structure  103 . In one embodiment, a spherical washer  118  is fitted over the spoke  105  and rests against the flared end  211  of the spoke  105 . Correspondingly shaped spherical recesses are formed in the hub flange or ring structure  103  to receive the spherical washer  118  and seat the spoke  105  under tension. 
     In addition, because the spherical washer  118  allows the spoke  105  to be in contact with the hub flange or ring structure  103  at various angles, the present structure (1) improves manufacturing flexibility (e.g., they are easy to fit and have a higher error tolerance) and (2) provides additional durability when operating the hub apparatus  200  at least because the spokes  105  are not rigidly secured to the hub flange or ring structure  103  at their ends. 
       FIG. 2 b    is an exploded view showing the hub apparatus  200  in accordance with embodiments of the present technology. The hub apparatus  200  includes the housing  101  (which has the sidewall  101   a  and the outer rim  101   b ) and the lid or cap  201 . On its outer surface, the housing  101  includes the hub flange or ring structure  103  configured to couple to a wheel/rim structure via multiple spokes. On its inner surface, the lid  201  includes multiple protrusions or stopping bumps  213  configured to stop the relative rotation (e.g., by cooperating with a motor locking device  400  discussed below with reference to  FIGS. 4 a -4 c   ) between the housing  101  and the stator assembly  208 . The multiple protrusions or stopping bumps  213  can be named as “engaging portions.” 
     In some embodiments, the engaging portion can be implemented as a recess (e.g., configured to receive the motor locking device  400 ), a hook (e.g., configured to engage the lock the motor locking device  400 ), and other suitable components. In some embodiments, the engaging portions are located either on the interior surface of either the sidewall  101   a  of the housing  101 , and/or on the interior surface of the lid  201 . The engaging portion and the motor locking device  400  together form a “locking mechanism” for the hub apparatus  200 . 
     In the illustrated embodiment, a support structure (or a chassis) formed as a spoked wheel (e.g., made of aluminum or other metal) is hollow in the interior and includes a flat rim opening, which multiple “oval-shaped” coils  108  are placed. Multiple magnets  221  (see e.g.,  FIG. 2 c   ) are circumferentially positioned on the inner surface of the outer rim  101   b,  and accordingly the housing  101  and the magnets  221  together act as a “rotor assembly” or a rotor in this embodiment. 
     The main circuit board  203  is configured to carry one or more controllers, controlling circuits, logic, sensors, wiring, and/or other suitable components necessary to apply current to the coils and to rotate the housing  101 . In some embodiments, the main circuit board  203  can carry an electrical control unit (ECU) of a vehicle (e.g., the ECU  902 ). In some embodiments, the main circuit board  203  can carry a power controller (e.g., a motor control unit, MCU  904 , not shown in  FIG. 2 b   ) configured to control the power output of the hub apparatus  200 . The power output can be measured in form of a measured torque force of rotation between the rotor assembly  222  (the housing  101  with the magnets  221  positioned therein or on its inner surface) and the stator assembly  208  or by the watts expended by the motor. In some embodiments, the main circuit board  203  can carry drive circuitry (e.g., the drive circuitry  905 ) configured to manage the power from a battery assembly  205  (e.g., to supply a three-phase alternating current). In some embodiments, the drive circuitry and the power controller can be integrated in one component (e.g., MCU). 
     The battery assembly  205  can include multiple battery packs. In the illustrated embodiments, the battery assembly  205  includes three battery packs laterally positioned adjacent to the main circuit board  203  in the interior space of the support wheel (or chassis). In other embodiments, the battery assembly  205  can have different numbers of battery packs arranged in various ways. In some embodiments, the battery assembly  205  can include three battery packs positioned at equal angles around the shaft  209  (e.g., to form a polygon such as a triangle, or different numbers of battery packs to form a rectangle, a pentagon, a hexagon, etc. in a reference plane generally perpendicular to the shaft  209 ). In some embodiments, the battery assembly  205  can be controlled or managed by a battery management system (BMS). The BMS can include one or more sensors configured to monitor the status of a battery. In some embodiments, the BMS can be positioned on the main circuit board  203 . In some embodiments, the battery packs (and battery cells therein) can be connected in series or in parallel, depending on various needs or actual designs. 
     In some embodiments, the battery assembly  205  can be coupled to one or more battery memories positioned on the main circuit board  203  and configured to store battery-related information from a processor related to usage statistics (e.g., battery usage information, battery operating instructions (such as charging/discharging rates or other instructions that may vary from different batteries), battery firmware, battery status, etc.). In some embodiments, the battery memory can also be configured to store vehicle information (e.g., an operating temperature in the hub apparatus  200 ) or user information (e.g., driving/riding history, habits, etc.). In some embodiments, the battery memories can be positioned inside a battery housing of the battery assembly  205 . 
     In some embodiments, the battery assembly  205  can be positioned inside the stator assembly  208  such that the hub apparatus  200  can have a compact design. Benefits of positioning the battery assembly  205  inside the stator assembly  208  include, for example, (1) the stator assembly  208  can protect the battery assembly  205 , for example, from impacts from the outside; and (2) this arrangement can at least partially prevent the battery assembly  205  from interference/influence of the magnetic field generated by the magnets of the rotor assembly  222 . 
     The main circuit board  203 , the battery assembly  205 , and the stator assembly  208  are fixedly coupled to the axle or shaft  209 . The shaft  209  can be coupled to a vehicular body (e.g., a frame, a chassis, structural parts, etc.) and support the same. During operation, the housing  101  and the wheel attached thereto (via the spokes coupled to the hub flanges) can rotate relative to the shaft  209  to move the vehicular body. In some embodiments, the shaft  209  can be coupled to a front wheel component (e.g., a front wheel fork) or a rear wheel component (e.g., a rear wheel frame). 
     In some embodiments, the hub apparatus  200  can include one or more waterproof components (e.g., O-rings) configured to make the hub apparatus  200  waterproof. In some embodiments, the waterproof component can be positioned at one or more locations such as a location adjacent to the shaft  209 , a location adjacent to other components of the hub apparatus  200 , etc. In some embodiments, the waterproof component can also be positioned between the housing  101  and the lid  201 , at one or both ends of the shaft  209 , between a side cover and the housing  101  and the lid  201 , etc. so as to enhance the overall waterproof capability of the hub apparatus  200 . 
     As previously described, in the embodiment that the system  900  is implemented as or integrated with the hub apparatus  200 , the stator assembly  208  and the rotor assembly  222  can be the stator and rotor of the motor  901 , respectively. The power supply  903  can be the battery assembly  205 . The MCU  904  and ECU  902  can be disposed on the main board  203 . The security unit  907  can be fixed at a chassis (e.g. chassis  301  shown in  FIG. 3 a   ) of the stator assembly  208 . 
       FIG. 2 c    illustrates how the stator assembly  208  is fitted within the housing  101 . As shown, the stator assembly  208  is coupled to the shaft  209  and then the shaft  209  is positioned to pass through a center opening  219  of the housing  101  (in direction N, as indicated). As shown, multiple permanent magnets  221  are positioned on the interior or inner surface of (the sidewall or the rim of) the housing  101 . During operation, the multiple permanent magnets  221  and the housing  101  can rotate (as a rotor) relative to the stator assembly  208 . 
     As shown in  FIG. 2   c,  the stator assembly  208  can include three sets of coils  108   a,    108   b,  and  108   c.  In the illustrated embodiments, each set of coils includes two subsets of coils positioned opposite to each other around the hub assembly  200 . As a result, the stator assembly  208  includes six subsets of coils positioned circumferentially around the shaft  209 . The coils  108   a,    108   b,  and  108   c  are configured to generate magnetic fields to rotate the magnets  221 . 
       FIG. 3 a    is a schematic diagram illustrating a stator assembly  208  in accordance with embodiments of the present technology. In the illustrated embodiments, the stator assembly  208  includes a number of coils  108  and a chassis  301  configured to be fixedly coupled to the shaft  209 . In the embodiments shown in  FIG. 3   a,  the coils  108  can include a first set of coils  108   a,  a second set of coils  108   b,  and a third set of coils  108   c.  The first set of coils  108   a  is configured to be coupled to the battery assembly  205  via a first wire  303   aa.  The second set of coils  108   b  is configured to be coupled to the battery assembly  205  via a second wire  303   bb.  The third set of coils  108   c  is configured to be coupled to the battery assembly  205  via a third wire  303   cc.  The first, second and third sets of coils  108   a - 108   c  are circumferentially positioned around the chassis  301  of the stator assembly  208  and are configured to receive (one phase of) a three-phase alternating current (AC) from the battery pack (e.g., via the drive circuitry  905 , as discussed above). 
       FIGS. 3 b  and 3 c    are partially schematic diagrams, illustrating a coil-based security mechanism having a security unit  907  in accordance with embodiments of the present technology. As shown in  FIGS. 3 b  and 3 c   , the security unit  907  includes a stopper  302 , a holder  304 , and an actuator  306  configured to move the stopper  302  in direction K. In the illustrated embodiments, the holder  304  is coupled to the stator assembly  208 . In the illustrated embodiments, three connectors  109   a,    109   b  and  109   c  are respectively coupled to the three sets of coils  108   a,    108   b  and  108   c.    
     The conductive plate  111  is positioned on the bottom surface of the stopper  302 . By this arrangement, when the stopper  302  is moved toward the three connectors  109   a,    109   b  and  109   c,  the conductive plate  111  causes a short circuit in the three sets of coils  108   a,    108   b  and  108   c.  Once the three sets of coils  108   a,    108   b  and  108   c  are short-circuited, if a user attempts to rotate a wheel driven by the motor  901  (e.g., rotating a rotor of the motor  901  by stepping on a pedal attached thereto; pushing/moving a bike having the wheel; letting the bike slip downhill, etc.), the magnets  221  positioned in the housing  101  rotate and induce a current in the coils causing a back electromagnetic field that opposes the magnetic force from the rotating magnets. 
     The induction currents in the short-circuited coils  108   a,    108   b  and  108   c  then generates a torque T in a reverse direction that can impede the rotor assembly  222  from rotating. Without being bound by theory, the torque T can be calculated based on the equations below. 
     
       
         
           
             
               
                 
                   V 
                   = 
                   
                     
                       k 
                       e 
                     
                      
                     ω 
                   
                 
               
               
                 
                   
                     ( 
                     1 
                     ) 
                   
                    
                   ↵ 
                 
               
             
             
               
                 
                   
                     V 
                     R 
                   
                   = 
                   I 
                 
               
               
                 
                   
                     ( 
                     2 
                     ) 
                   
                    
                   ↵ 
                 
               
             
             
               
                 
                   
                     Ik 
                     T 
                   
                   = 
                   T 
                 
               
               
                 
                   
                     ( 
                     3 
                     ) 
                   
                    
                   ↵ 
                 
               
             
           
         
       
     
     In Equations (1), (2) and (3) above, “V” represents voltage, “ω” represents rotational speed, “R” represents resistance (of the coils  108   a - c,  for example), and “I” represents electric current. “K e ” and “K T ” are constants. 
     According to Equation (1), when a user attempts to rotate the rotor of the motor  901  (i.e., it generates rotation speed w), a certain amount of voltage V can be generated in the coils  108   a,    108   b  and  108   c.  The faster the rotor rotates, the larger amount of voltage V is generated. Since the coils  108   a,    108   b  and  108   c  are short-circuited, the generated current I (from generated voltage V, according to Equation (2) above) flows back to the coils  108   a,    108   b  and  108   c  (e.g., from one coil to another coil). According to Equations (2) and (3), the generated voltage V can cause the torque T opposite to user&#39;s action. The generated torque T can be used to prevent the rotor from rotating and therefore can be acting as a security and anti-theft mechanism. 
     Advantages of the security mechanism include that (1) it can operate when the power of the hub apparatus  200  is turned off (e.g., the security mechanism can function without a power supply); (2) it can generate torque in response to user actions (i.e., the faster a user rotates the rotor, the larger amount of torque can be generated to counter the rotation); (3) it can be applied to various types of wheels; (4) it can coexist with other locking devices (e.g., a physical locking device  400  to be discussed below). 
     In some embodiments, less than all of the coils shown as two of the coils  108   a,    108   b  and  108   c  can be short-circuited. In such embodiments, the conductive plate  111  can be configured/positioned to only short-circuit two of the coils  108   a,    108   b  and  108   c  by only contacting two of the connectors  109   a,    109   b  and  109   c.  In some embodiments, the stopper  302  can be made of a conductive material such that the stopper  302  can directly short-circuit two or more of the coils  108   a,    108   b  and  108   c.    
     In the present embodiment, the rotor assembly  222  of the hub apparatus  200  (or the rotor assembly of the motor  901 ) is fixedly disposed in the wheel. In some embodiments, the hub apparatus  200  and the motor  901  are configured to power a wheel of the vehicle via power transmission components like belt, chain, gear sets etc. There can be a gear reduction ratio between the rotor assembly and the wheel. More particularly, the rotor assembly and the wheel do not necessary have the same rotational speed (but in proportion to each other). For example, there can be a “gear-reduction” ratio between the rotor assembly of the motor  901  and the wheel driven by the rotor. For example, a “1:6” gear-reduction ratio means when the rotor assembly rotates 360 degrees (e.g., a circle), the wheel only rotates 60 degrees (e.g., ⅙ of the circle). One advantage of the present security mechanism is that it can generate torque to prevent or impede unauthorized action in proportion to the gear reduction ratio. In other words, for vehicles with higher gear reduction ratios, the present security mechanism can generate larger torque accordingly. 
     In the embodiments that the power transmission components include a gear set, the gear set can be configured as follows. Traditionally, when the vehicle is parked, the gear set is shifted to “P position” or “Parking position” (where the gear set disengages from the rest of the power transmission components such as a chain) by a shift lever and the gear set can be locked. In order to utilize the technology disclosed in the present disclosure, the gear set needs to be shifted to “D position” or “Driving Position” (where the gear set engages the rest of the power transmission components) or change the configuration of the gear set in “P position” such that the gear set still engages the rest of the power transmission components in “P position.” 
     It is also noted that in the above-described embodiments where the motor  901  is configured to power a wheel of a vehicle via power transmission components, the security unit  907  is not disposed inside the motor  901  (as shown in embodiments corresponding to  FIG. 2 a -3 c   ). In such embodiments, the security unit  907  can be disposed (or appended) between the MCU  904  and the motor  901  of the vehicle. 
     In some embodiments, the present security mechanism can include an additional locking device by engaging the rotor of the motor  901 , when the motor  901  is turned off or has been turned off for a period of time, so as to make rotating the rotor even more difficult. In some embodiments, the present security mechanism can include physical locking devices, as discussed in  FIGS. 4 a -4 c    below. 
       FIG. 4 a    is an exploded view of a motor locking device  400  in accordance with embodiments of the present technology. The motor locking device  400  is configured to lock a motor (e.g., the motor  901 ; by preventing a rotor of the motor  901  from rotating relative to a stator of the motor  901 ) of a hub apparatus (e.g., the hub apparatus  200 ). 
     As shown in  FIG. 4   a,  the motor locking device  400  includes a stopper  401 , a stopper holder  403 , an actuator  406  coupled to a rod (or a screw/threaded rod)  407 , and a plug  409  configured to connect wires of the actuator  406  to a controller that supplies current to move the rod  407 . The stopper holder  403  is fixedly attached to the stationary part (e.g., a stator) of an electric motor positioned inside the hub apparatus. The stopper  401  is positioned in the stopper holder  403  and is configured to be moved by the rod  407 . 
     In some embodiments, a positioning component such as a threaded nut  411  is placed in an enclosure of the stopper  401  and biased with a spring  413 . The rod  407  can be threaded and rotated by the actuator  406 . The threaded rod  407  moves the nut  411  up and down on the threaded rod  407  to advance or retract the stopper  401  in and out of engagement with a surface on the rotor (e.g., the housing  101  of the hub apparatus  200 ). In some embodiments, the actuator  406  can be an axial solenoid valve, a linear motor, or another suitable actuator that moves the stopper  401 . 
     In some embodiments, the spring  413  can be positioned to provide a resilient force to the stopper  401  to hold the stopper  401  to the nut  411  such that movement of the nut  411  relative to the rod  407  moves the stopper  401  toward or away from the inner surface of a housing (e.g., the housing  101 ). In some embodiments, the stopper  401  can be positioned adjacent to the inner surface of the housing without (actually) contacting it. 
     In some embodiments, the plug  409  can be coupled to a controller coupled to an electric control unit (ECU) (e.g., the ECU  902 ) and/or other suitable devices. In some embodiments, the ECU can lock/unlock the motor in response to a signal from an external device (e.g., a smartphone, a key fob, etc.). In some embodiments, the ECU can lock/unlock the motor without receiving a signal from an external device (e.g., a smartphone, a key fob, etc.) for a predetermined period of time (e.g., 10 minutes after the motor is turned off). 
       FIGS. 4 b  and 4 c    are sectional and isometric views of the motor locking device  400 , showing the operation thereof. As shown, the stopper holder  403  of the motor locking device  400  is fixedly coupled to a stator assembly  208  such that a rotor assembly  222  is free to rotate (e.g., about axis R as indicated in  FIG. 4 c   ) relative to the motor locking device  400 . 
     In the illustrated embodiments shown in  FIG. 4   c,  the rotor assembly  222  includes the housing  101  and a number of magnets  221  attached thereto. In the illustrated embodiments, the stator assembly  208  includes a number of coils  108 . As shown in  FIG. 4   c,  two stopping bumps  405   a,    405   b  are coupled to (or integrally formed with) the inner surface of the housing  101 . The stopping bumps  405   a,    405   b  are configured to restrain the rotor assembly  222  (e.g., the housing  101  and the magnets  221 ) from rotating relative to the stopper  401  (which is fixed coupled to the stator assembly  208 ), when the stopper  401  is in an extended, “locked” position ( FIG. 4 c   ). 
     When the stopper  401  is retracted in an “unlocked” position (e.g., as shown in  FIG. 4 b   ), the rotor assembly  222  can rotate relative to the stopper  401  (and the stator assembly  208 ). In some embodiments, there can be more than two stopping bumps coupled to the outer housing  201  so that the wheel can be locked at a number of different positions. 
     In  FIG. 4   b,  the motor locking device  400  is in an “unlocked” position, and the rotor assembly  222  can rotate relative to the stator assembly  208 . In such embodiments, (an edge of) the stopper  401  is flush with (an outer edge of) the stopper holder  403  and therefore the stopper  401  does not contact the stopping bumps  405   a,    405   b  when rotating. 
     When the ECU (e.g., the ECU  902 ) instructs the actuator  406  to rotate the rod  407  (e.g., to move the stopper  401  in direction M shown in  FIGS. 4 b  and 4 c   ), the wheel is locked and unlocked accordingly. 
     Once the stopper  401  is moved toward the housing  101  (e.g., in direction M), as shown in  FIG. 4   c,  the stopper  401  is no longer flush with the stopper holder  403 , and the motor locking device  400  is at a “locked” position. Accordingly, the stopper  401  is “stopped” or restrained by one of the stopping bump  405   a,    405   b  and cannot freely rotate relative to the rotor assembly  222 . As a result, the rotor assembly  222  is locked and cannot rotate relative to the stator assembly  208 . 
     In some embodiments, the stopping bumps can be circumferentially positioned at the inner surface of the housing  101 . In such embodiments, the stopper  401  can be stopped by any one of the stopping bumps. In some embodiments, the stopping bumps can be formed in various shapes such as, a protrusion, a block, and/or other suitable shapes that can be engaged the stopper  401  when it is in the extended position. 
     In some embodiments, the stopping bumps can be made of a relatively-easy replaceable material such as plastic, whereas the stopper  401  can be made of a relatively hard or stiff material. In such embodiments, when one or more of the stopping bumps are damaged or have failed (e.g., caused by contacting the stopper  401 ), the rest of the stopping bumps can still engage the stopper  401  and lock the position of the rotor assembly  222 . It is easy and convenient to replace a damaged stopping bump. As a result, the present technology provides a reliable, easy-to-maintain, mechanism to lock, stop, and/or control the rotation of an electric motor. 
       FIG. 5  is an isometric view of a vehicular frame  501  supporting a hub apparatus (e.g., hub apparatus  200 ) in accordance with embodiments of the present technology. As shown, the shaft  209  of the hub apparatus  200  is fixedly coupled to the vehicular frame  501 . The housing  101  of the hub apparatus  200  is coupled to a wheel  503  via the spokes  105  and the hub flange or ring structure  103  (as shown, a side cover  502  can be attached to the hub apparatus  200 ). The wheel  503  can be rotated by the hub apparatus  200  to move the vehicular frame  501 . When the wheel  503  is not rotating, a charging head  505  can be coupled to the hub apparatus  200  and charge the same. In some embodiments, the charging head  505  can be coupled to the hub apparatus  200  by a magnetic force. As shown, the charging head  505  can be coupled to a power source (e.g., mains electricity) via a wire  507 . In some embodiments, the wheel  503  can be a wheelset having a tire  509 , a wheel rim  511 , multiple spokes  105 , and the hub apparatus  200 . 
     In some embodiments, when the hub apparatus  200  starts to be charged by the charging head  505 , the ECU  902  can instruct the security unit  907  to short-circuit the coils  108 . In some embodiments, when the ECU  902  receives a signal indicating that the charging process is complete, the ECU  902  can instruct the security unit  907  to move the coils  108  back to their normal, working condition (e.g., not short-circuited). 
     In some embodiments, the security unit  907  and the locking device  400  can share the same actuator. For example, the actuator  306  for the security unit  907  ( FIG. 3 b   ) and the actuator  406  for the locking device  400  can be the same component. For example, a solenoid valve can be configured to move both the stopper  302  and the stopper  401 . 
       FIGS. 6 and 7  are flowcharts illustrating methods  600  and  700  performed by a programmed processor, controller, or other logic circuit in accordance with embodiments of the disclosed technology. The methods  600  and  700  are configured to manage a security system/mechanism in accordance with the present technology. In some embodiments, the methods  600  and  700  can be implemented (1) in a powertrain assembly; (2) in a vehicle system; (3) a hub apparatus; and (4) a system having a motor with a rotor and a stator, for example, the systems and apparatuses shown in  FIG. 1 a   - 5 . 
     Referring to  FIG. 6 , the method  600  starts at block  601  by receiving, e.g., by a controller, a first signal indicating that a motor is turned off (e.g., a user operates a switch to turn off the motor). In some embodiments, the controller can be an electric control unit (e.g., ECU  902 ) of a vehicle. In other embodiments, the controller can be a processor in a portable device (e.g., a smartphone) of a user. In some embodiments, the first signal can be communicated via various wired or wireless connections. 
     At block  603 , the method  600  continues by sending, by the controller, a second signal to instruct a security unit (e.g., security unit  907 ) to short-circuit part or all sets of coils of the motor. When the part or all sets of coils are short-circuited, the motor is locked by the “coil-based” security mechanism or system (e.g., system  900 ) disclosed in the present application. In some embodiments, the method  600  can include activating a physical locking device (e.g., locking device  400 ) so as to enhance security of the motor. 
     At block  605 , the controller instructs the security unit to restore the power connection of the part or all short-circuited coils. The motor is then “unlocked” and can be operated (e.g., to drive a vehicle). The method  600  then returns for further process. 
     Referring to  FIG. 7 , the method  700  starts at block  701  by receiving, by a controller, a first signal indicating that a motor is turned off (e.g., a user operates a switch to turn off the motor). In some embodiments, the controller can be an electric control unit of a vehicle. In other embodiments, the controller can be a processor in a portable device (e.g., a smartphone) of a user. At block  703 , the method  700  continues by sending, by the controller, a second signal to instruct a security unit to short-circuit part or all sets of coils of the motor. In some embodiments, the first and second signals can be communicated via various wired and/or wireless connections. 
     At block  705 , the controller instructs a circuit controller (e.g., the circuit controller  906  of the MCU  904 ) to send a testing signal to verify whether the coils have been short-circuited. At decision block  707 , the method  700  determines whether the controller can receive a confirmation that the coils are short-circuited (e.g., from the circuit controller  906  of the MCU  904 ) within a predetermined time period (e.g., 0.1-5 seconds). 
     If the determination at block  707  is affirmative, then the process goes to block  709 , where the controller enters a hibernation mode. If the determination at block  707  is negative (which means the confirmation (e.g., a confirmation signal) is not successfully received by the controller), then the process goes to block  711 , where the controller notifies a user (e.g., sending a notification to a user mobile device or a display on the vehicle) about the failure of receiving confirmation (or the failure of confirmation), and then the controller enters a hibernation mode. In some embodiments, the controller can instruct other components (e.g., the circuit controller) to go hibernate as well. The method  700  then returns for further process. In some embodiments, the circuit controller can enter a hibernation mode itself after sending the confirmation to the controller. 
     In some embodiments, the method  700  can include activating a physical locking device (e.g., locking device  400 ) so as to enhance security of the motor. In some embodiments, the process of activating the physical locking device can be performed at block  709  or block  711 . In other embodiments, the process of activating the physical locking device can be performed at block  701 . In some embodiments, the user can receive a notification when the physical locking device is activated/enabled. 
     In some embodiments, the method of the present disclosure can include, for example, (1) receiving, by a controller, a signal regarding turning off the vehicle; (2) instructing, by the controller, a security unit to short-circuit a plurality of coils of a motor in the vehicle; (3) instructing, by the controller, a circuit controller to send a testing signal verify whether the plurality of coils are short-circuited; and (4) entering a hibernation mode when receiving a confirmation signal that the plurality of coils are short-circuited. In some embodiments, the method can include instructing, by the controller, the circuit controller to hibernate. In some embodiments, the method can include activating, by the controller, a locking device by instructing an actuator of the locking device to move a stopper of the locking device to contact a rotor assembly of the motor of the vehicle, when the controller does not receive the confirmation signal that the plurality of coils are short-circuited. In some embodiments, the locking device can be activated when receiving the signal regarding turning off the vehicle. 
     Although the present technology has been described with reference to specific exemplary embodiments, it will be recognized that the present technology is not limited to the embodiments described but can be practiced with modification and alteration within the spirit and scope of the appended claims. Accordingly, the specification and drawings are to be regarded in an illustrative sense rather than a restrictive sense.