Patent Publication Number: US-2021174995-A1

Title: Servo-actuated rotary magnetic latching mechanism and method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional patent Application No. 62/585,018, filed on Nov. 13, 2017, entitled “SERVO-ACTUATED LATCHING MECHANISM FOR PASSIVE MAGNETS,” and U.S. Provisional Patent Application No. 62/663,372, filed on Apr. 27, 2018, entitled “SERVO-ACTUATED ROTARY MAGNETIC LATCHING MECHANISM AND METHOD,” the disclosure of which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     Technical Field 
     Embodiments of the subject matter disclosed herein generally relate to a magnetic latching mechanism, and more specifically, to methods and systems for allowing robots to magnetically latch to each other and be able to easily separate from the magnetic grip of each other. 
     Discussion of the Background 
     Magnetic latching with its wide applications have been around for years. From decades ago to even recent years, extended research has been performed to develop a reliable, small and low-power consumption magnetic latching mechanism. There is no better latching mechanism then a magnetic one when considering the reliability and consistency with which the magnets interact with each other as well as with other ferrous objects. In the modern world, the magnets come in different variants, e.g., permanent magnets, electromagnets, and electropermanent magnets (EPMs) being the three main classes. Out of these three classes, the permanent magnets perform best in terms of power consumption (practically there is no power consumption), scalability and latching strength (see  FIG. 1 , where black indicates poor, gray indicates best, and white indicates acceptable). The part where the permanent magnets perform poorly comparative to the electromagnets and the EPMs is the latching control. 
     It is clear from  FIG. 1  that the permanent magnets are the most economical and efficient form to use in miniature and small sized applications, where power consumption has to be kept at a minimum. However, the permanent magnets provide no control over their superior latching capabilities, i.e., there is no turn off signal that can be used to simply break or detach the latched components in an assembly. 
     Some methods have been used in recent years for achieving programmable, self-assembly, robots that use the strength of permanent magnets to perform autonomous latching tasks. Most of these methods utilize either electro-magnets or EPMs, which have the drawbacks of high power consumption and customized design requirements. For power efficient applications, the use of electromagnets is ruled out because of their hunger for power. For EPMs, there are other problems, such as, the lack of strong bonding (˜ in the order of Newtons) that is necessary for any application of practical/industrial interest. Another drawback of the existing magnetic latching mechanisms is the possible introduction of interference in local communication caused by the on/off latching activity of the EPM control circuit, which is basically a high frequency RC circuit (see, for example, Lily Robots, Mota Group, or the Pebbles robot at MIT). 
     Some research groups have however, used permanent magnets for strong bonding purposes (see, for example, the M-blocks at MIT), but their usefulness has only been in the making of the bonds. They have used a momentum driven, brushless motor mechanism for breaking the contact between two parties latched through the magnetic interaction of the permanent magnets, which is not as smooth or much of a direct breakage. Also the breakage for these robots involves the rotation of the whole agent (robot or bot) around one of its axis, which completely changes its orientation during a disassembly action. 
     However, in many applications, e.g., latching, perching, etc. in air using drones, rotating the entire robot is not desirable and sometimes not possible. A good magnetic latching mechanism is desired to have a very smooth detachment (undocking) of the latched components. Also, the face magnets for the M-blocks robots are placed at fixed positions and are static in nature, i.e., they are unable to change their polarity or position and thus, the bots have to pay a price in terms of their abrupt change in orientation for executing a bond break. 
     Therefore, there is a need for a magnetic latching mechanism that uses permanent magnets but at the same time exhibits a smooth undocking operation, without rotating the entire robot or bot. 
     SUMMARY 
     According to an embodiment, there is a magnetic latching mechanism that includes a servo-motor configured to rotate an axle, a latching rotor attached to the axle and configured to rotate, and a pair of latching permanent magnets attached to the latching rotor. A north pole of a permanent magnet and a south pole of another permanent magnet of the pair are facing along a same direction. 
     According to another embodiment, there is a robot that includes a frame, a magnetic latching mechanism, a processor that controls the magnetic latching mechanism, and a power source for powering the processor and the magnetic latching mechanism. The magnetic latching mechanism uses permanent magnets for bonding or unbonding to another device. 
     According to still another embodiment, there is a method for bonding and debonding a first robot with a second robot. The method includes a step of providing the first and second robots at a given distance D, a step of reducing the distance D between the first and second robots, a step of bonding the first robot with the second robot due to attraction magnetic forces developed between a magnetic latching mechanism of the first robot and a magnetic latching mechanism of the second robot, a step of rotating a latching rotor of the magnetic latching mechanism of the first robot relative to a latching rotor of the magnetic latching mechanism of the second robot to generate a repelling magnetic force, and a step of unbonding the first robot from the second robot. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate one or more embodiments and, together with the description, explain these embodiments. In the drawings: 
         FIG. 1  illustrates various capabilities of permanent and active magnets; 
         FIGS. 2A and 2B  show a robot having side faces that include corresponding magnetic latching mechanisms; 
         FIG. 3  shows the internal configuration of a robot and its magnetic latching mechanism; 
         FIGS. 4A to 4C  show the components of a magnetic latching mechanism; 
         FIG. 5  is a flowchart of a method for bonding and unboding two robots having corresponding magnetic latching mechanisms; 
         FIGS. 6A and 6B  show two magnetic latching mechanisms belonging to two different robots; 
         FIGS. 7A to 7D  show how two robots bond and then unbond due to their magnetic latching mechanisms; and 
         FIG. 8  is a table indicating the various components used for a given robot having a magnetic latching mechanism. 
     
    
    
     DETAILED DESCRIPTION 
     The following description of the embodiments refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. The following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims. The following embodiments are discussed, for simplicity, with regard to small robots (also called bots) that are capable of docking and undocking from each other. However, the invention is not limited to such embodiments, as other types of robots or devices (e.g., drones) may be provided with the magnetic latching mechanism discussed herein. 
     Reference throughout the specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrases “in one embodiment” or “in an embodiment” in various places throughout the specification is not necessarily referring to the same embodiment. Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments. 
     According to an embodiment, there is a novel magnetic latching mechanism that achieves docking and undocking for permanent (also called passive because of its zero power consumption) magnets. In this embodiment, an indirect way for controlling the latching of the permanent magnets is achieved. The mechanism may use ultra-nano servo actuators for the undocking of the magnets. A generic purpose of this latching mechanism is to enable strong bond making and bond breaking abilities among the magnetic contacts in any given assembly that has latching components. In one application, the proposed mechanism is applied, as discussed later, in the specific application of programmable self-assembly devices, where small scale robots (in the cm range), called usBots, can autonomously interact and collaborate with each other to form a desired target assembly. 
     Details about this novel magnetic latching mechanism are now discussed.  FIGS. 2A and 2B  show a robot  200  being shaped as a cube. Other shapes may be used for the robot. Robot  200  has a top face  202 A and a bottom face  202 B, opposite to the top face  202 A. Because the intention of this embodiment is not to change the robot&#39;s top and bottom faces (due to a change in the spatial orientation of the robot), the top and bottom faces do not have a magnetic latching mechanism. 
     Robot  200  also has four side faces  210 A to  210 D, only two of which are shown in  FIGS. 2A and 2B . Each of these faces may have a corresponding magnetic latching mechanism  220 A and  220 B. While the embodiment discussed herein considers that each side face has a magnetic latching mechanism, one skilled in the art would understand that it is possible that only one, or only two or only three side faces of the robot may have the magnetic latching mechanism. 
       FIG. 3  shows the robot  200  being opened up so that various internal components are visible. This figure shows each of the faces  210 A to  210 D. In one application, a frame  212  may be used to support the side faces  210 A to  210 D but also the top and bottom faces  202 A and  202 B. The robot  200  includes a processor (e.g., a microcontroller)  204  located on a servo mount  206 . Attached to the servo mount  206  (which may be a frame, bracket, etc.) are one or more servo-motors  208 A and  208 D. In this embodiment, each latching mechanism has its own servo-motor so that each latching mechanism operates independent of the other latching mechanism. Servo-motor  208 A has an axle  209 A that connects to a latching rotor  214 A through a servo to rotor mount  216 A. The rotor mount  216 A may be attached directly to the latching rotor  214 A. In one application, the latching rotor  214 A has a groove in which the rotor mount fits. In still another application, the latching rotor has a cut through in which the rotor mount fits. In one embodiment, the axle  209 A can be directly connected to the latching rotor  214 A. If each side face  210 A to  210 D has a corresponding latching rotor, then each latching rotor is connected to a corresponding servo-motor for ensuring independent rotation of the latching rotors. Note that side face  210 A, which hosts the latching rotor  214 A, has a large hole centered within the side face, for receiving the latching rotor  214 A. A small clearance is formed between the hole in the side face  210 A and the latching rotor  214 A so that the latching rotor can easily rotate. 
     Each latching rotor  214 A has one or more pairs  218  of permanent magnets  218 A- 1  and  218 - 2  attached to it. The latching magnets  218 A- 1  and  218 A- 2  are attached on the back side of the latching rotor  214 A and for this reason, the latching magnets  218 A- 1  and  218 A- 2  are illustrated with dashed lines in the figure.  FIG. 3  shows a pair  218 C of latching magnets attached to the back of the latching rotor  314 C. As will be discussed later, the latching magnets attached to each latching rotor are provided in pairs. The servo-motor  208 A, latching rotor  214 A, rotor mount  216 A and a pair of latching magnets  218 A form the magnetic latching mechanism  230 A. 
       FIG. 3  further shows one or more light emitting diodes (LED)  220 . In one application, each side face  210  has a corresponding LED  220 . The LED  220  may be used for inter-robot communication. As two different robots approach each other for docking, one or more alignment magnets  222  may be distributed over one or more of the side faces  210 . For example,  FIG. 3  shows each side face having four pairs of alignment magnets  222 . The alignment magnets  222  are permanent small magnets and each pair has the corresponding magnets arranged so that one magnet of the pair has the north pole facing outward and the other magnet of the pair has the south pole facing outward. In this way, when two different side faces of two different robots are approaching each other, these alignment magnets force the robots to get aligned to each other. Note that these robots may have no means for moving from one point to another point. This feature would be discussed in more detail later. 
       FIG. 3  also shows side closure magnets  224  located on the inside of the side faces  210 . The closure magnets may be permanent magnets and may come in pairs. These magnets may be magnetically attracted to the frame  212  so that there is no need for screws or other means for attaching the faces of the robot to its frame. Alternatively, the magnets from one side face may mate directly with magnets from an adjacent side face to form the body of the robot. An ambient light sensor  226  may be placed on one or more of the side faces  210 . When this sensor receives light from the LED  220 , it generates a signal that is transmitted to the processor  204 . This is one way for two robots to exchange information, i.e., use light for transmitting one or more bits of information. Each processor  204  may store in a memory a table that translates each sequence of light signals into a command so that a meaningful communication between the robots can take place. The robot may also include a power source  228  (for example, a battery) for providing the necessary energy to the LED for generating light and to the processor for performing various commands and instructions. Note that the robot discussed herein has no locomotion. However, one skilled in the art would understand that a locomotion mechanism may be provided to each robot if so desired. 
     The magnetic latching mechanism  230 A is shown in more detail in  FIGS. 4A to 4C , which are now discussed.  FIG. 4A  shows the servo mount  206  and two magnetic latching mechanisms  230 A and  230 B. Note that the associated side faces of the latching mechanisms (each side face may have its own latching mechanism  230 ) are not shown in this figure for simplicity. However, if the side face  210 B would be added in  FIG. 4A , it would fit around the latching rotor  214 B so that that mechanical brakes  217 B extend behind the side face  210 B. In other words, the mechanical brakes are not visible from outside when robot  200  is fully assembled. While the axle  209 A, latching rotor  214 A and rotor mount  216 A are visible in the figure, the associated pairs of latching magnets are not visible, as they are attached behind the latching rotor  214 A. However, the latching magnets  218 A- 1  to  218 A- 4  are shown with dash lines in the figure.  FIG. 4B  shows the back side of the latching rotor  214 A and two pairs  218   1  and  218   2  of latching magnets. Note that each pair of latching magnets have the N and S poles opposite to each other and also the poles are facing toward the outside of the robot. 
     Both  FIGS. 4A and 4B  shows the latching rotor  214 A having two mechanical brakes  217 A. In one application, the latching rotor has only one mechanical brake. The mechanical brake may be a planar extension of the latching rotor, i.e., a tab. These mechanical brakes are used to ensure that a rotation of the latching rotor does not extend past a given angle, as discussed later.  FIG. 4A  also shows a profile of the latching rotor  214 B, its mechanical brakes  217 B and the corresponding servo-motor  208 B, which rotates the latching rotor. Note that the latching rotor  214 B may be rotated independent of the latching rotor  214 A, as each latching rotor has its own servo-motor. The profile of the latching rotor  214 B shows that the latching magnets  218 B- 1  are embedded into a thickness of the latching rotor. In one embodiment, a surface of the latching magnet is flush with a back side of the latching rotor  214 B, or flush with a front side of the latching rotor  214 B. In one application, all surfaces of the latching magnet are inside the latching rotor. In one application, a shielding layer  232  may be placed to separate the latching magnet  218 B- 1  from a mating magnet from another robot.  FIG. 4C  shows the device of  FIG. 4A  rotated by 180 degrees. In one application, the servo mount  206  may have a first part  206 A, as illustrated in  FIG. 4C , configured to hold only two magnetic latching mechanisms  230 A and  230 B and a second part (not shown but symmetrical to first part  206 A) of the servo mount  206  may be configured to hold the other two magnetic latching mechanism. The two parts may be connected together to form the servo mount  206  and then they can be placed inside the frame  212 . 
     An interaction (docking and undocking) between the magnetic latching mechanisms of two different robots is now discussed with regard to  FIG. 5 .  FIGS. 6A and 6B  show only the latching rotors  214 A and  214 A′ of two different robots  200  and  200 ′ and their corresponding servo-motors  208 A and  208 A′.  FIG. 6B  also shows the latching rotor  214 A′ having two pairs  218   1 ′ and  218   2 ′ of latching magnets distributed across the latching rotor  214 A′ in a symmetric way. If the top and bottom faces and the side faces would be added to these two robots, the same configuration would look like what is shown in  FIGS. 7A and 7B . The configuration shown in  FIG. 7A  has the two robots  200  and  200 ′ spaced apart by a distance D, which is large enough so that there is no substantial magnetic force acting on one robot because of the other. Thus, in step  500 , two robots  200  and  200 ′ are provided on a surface of a platform  700  as shown in  FIG. 7A . Note that the two robots do not have locomotion means. However, as already discussed above, one skilled in the art would know how to add locomotion to these robots if necessary. The platform  700  may move (e.g., tilt or shake) so that the distance D may vary. If the distance D increases, nothing happens with the two robots. However, if the distance D decreases in step  502 , the magnetic force (attraction or repulsion) between the two robots starts to increase. 
     Supposing that the two latching rotors are oriented so that each latching magnet from latching rotor  214 A is facing an opposite magnetic pole of the corresponding latching magnet of latching rotor  214 A′, as illustrated in  FIG. 6B , then a magnetic force between the two latching rotors becomes stronger and the two robots start to move toward each other, due to this attraction force. Note that even if the two latching rotors are not perfectly aligned, as the two rotors get closer and closer, they automatically align to each other in step  504  because of the alignment magnets  222  shown in  FIG. 3 . The alignments magnets  222  force the two latching rotors  214 A and  214 A′, and implicitly the two side faces  210 A and  210 A′ that host the latching rotors to align to each other. In one application, the alignment action means that the axles  209 A and  209 A′ of each servo-rotor  208 A and  208 A′, respectively, are substantially (i.e., about 10%) extending along a same axis X, as shown in  FIG. 6A . 
     In step  506 , the two robots get in contact with each other due to the attraction forces generated by the latching magnets. In fact, the two latching rotors  214 A and  214 A′ may contact each other as shown in  FIG. 7C . In this state (the docked state), the latching magnets from one latching rotor are fully aligned with the latching magnets from the other latching rotor and each pole of each latching magnet is directly facing (with a small gap to be discussed later) an opposite pole of a latching magnet from the other robot. Further, the latching magnets of each latching rotor are symmetrically distributed along their latching rotor and the two latching rotors of the two robots are substantially identical so that the latching magnets from the two latching rotors are aligned to maximize the magnetic force between them. In other words, the distribution of the latching magnets of a latching rotor of a first robot is a mirror version of the distribution of the latching magnets of a latching rotor of a second robot. In one embodiment, this configuration is repeated for each side face of each robot. 
     At this time, the light emitting sensor  220  from one robot is directly facing the light ambient sensor  226  of the other rotor so that, in step  508 , signals and/or commands can be transmitted from one robot to another. Thus, communication between the two robots may be established in step  508 . However, one skilled in the art would understand that this communication is not necessary for docking or undocking the two robots. In one application, the processor of one robot can communicate via the light emitting sensor  220  and the light ambient sensor  226  with the processor of the other robot. Also note that  FIGS. 5 to 7D  describe the docking and undocking of two robots  200  and  200 ′. However, the same steps may be applied to plural robots so that a chain of robots are docked together and communication between plural robots may be established through the light emitting sensors and the light ambient sensors discussed above. 
     When the processor of one robot, e.g., robot  200 , decides to undock from the other robot  200 ′, the processor  204  instructs the corresponding servo motor  208 A to rotate in step  510  the latching rotor  214 A, with a given angle relative to its axle  209 A, and implicitly, relative to the latching rotor  214 A′. If the rotation angle is selected to be 90°, then, the latching magnets of one robot become again aligned with the latching magnets of the other robot, but this time, each pole of the first robot is facing a same pole of the opposite robot, which means that a repealing magnetic force appears between the two side faces  214 A and  214 A′ of the robots  200  and  200 ′. Because the latching magnets are selected to have stronger magnetic forces between them than the alignments magnets, the two robots undock in step  512  due to the large repealing forces. At this time the distance between the two side faces of the two robots increases as illustrated in  FIG. 7D  and separation of the two robots is achieved. 
     Note that  FIG. 7C  shows the braking mechanism  217 A of the latching rotor  214 A pointing North while  FIG. 7D  shows the same braking mechanism  217 A pointing West. This denotes that the latching rotor  214 A has rotated with 90 degrees.  FIG. 7D  also shows a stop break  219 A attached to the back of the side face  210 A and this stop break stops the rotation of the braking mechanism  217 A in case that the servo-motor  208 A fails to rotate the latching rotor by exactly 90 degrees. In one embodiment, if the two robots  200  and  200 ′ agree through the communication established in step  508  to both undock, it is possible that each robot turns its latching rotor with 45 degrees in opposite directions, so that a total relative rotation of one latching rotor relative to the other is about 90 degrees, enough to generate the repealing magnetic forces discussed above. One skilled in the art would understand that even a rotation smaller than 90 degrees (e.g., 45 degrees or larger) may achieve the undocking of the robots. 
     The repulsive or attraction magnetic force used to dock and undock the robots is now discussed. If a ferrous object is in close vicinity (from a few mm to few cm, depending on the object) to a permanent magnet, there exists a force of attraction between the object and the magnet. Mathematically, the force of attraction of a magnet at its air gap (the space around the poles of a magnet) is given by Maxwell equation: 
     
       
         
           
             
               F 
               = 
               
                 
                   
                     B 
                     2 
                   
                    
                   A 
                 
                 
                   2 
                    
                   
                     μ 
                     0 
                   
                 
               
             
             , 
           
         
       
     
     where F is the force (N), A is the surface area of the pole of the magnet (m 2 ), B is the magnetic flux density (T), and μ 0  is the permeability of the medium (air in this case). 
     Thus, if the target is a magnet itself, then there exists either a force of attraction or repulsion between the two magnets. The nature of this force depends on the polarity of the two approaching magnets. Nevertheless, this force is almost twice (in case of neodymium magnets) as compared to the magnetic force given by the above equation. This concept in used in the above embodiments to achieve programmable self-assembly in small robots. As shown in  FIGS. 3 and 7D , in the latching rotor, the magnetic polarities (or poles) of adjacent latching magnets, along the circumference of the latching rotor, are kept to alternate from one magnet to another one. 
     In this way, a complete reversal of all latching magnets&#39; polarity can be achieved by a 90 degrees rotation of one latching rotor relative to another latching rotor, as illustrated in  FIGS. 7C and 7D . Note that the rotation can be either clockwise or counter-clockwise. This concept has been proven to be very effective. 
     Thus, after two robots approach each other as shown in  FIGS. 7A and 7B , they are going to be attracted towards each other with a force roughly eight times the pull of a single latching magnet (assuming that each latching rotor has four individual latching magnets). This bond formed among the robots&#39; side faces is strong and yet not permanent because the bond can be easily (i.e., with low energy) be undone by using the servo-motor to perform a 90 degrees rotation of one latching rotor, by either of the robots or a 45 degrees rotation of each of the robots. 
     One matter associated with this magnetic latching mechanism is that the action of bond breaking (i.e., the undocking) by revolving either or both of the latching rotors require a mechanism that produces a high torque. In one embodiment, due to small size constraints on the robot design, and difficulty of finding small size and high torque servos, it is possible to introduce a shielding layer on either sides of the bonding faces of the latching magnets. This shielding layer may have various sizes, for example, 1 mm thickness. The shielding layer (for example, plastic layer) decreases the magnetic force of attraction to about 8 N in total. At this level, the bond between two latching rotors facing each other and in contact with each other can be broken by a 90 degrees rotation achieved with the smallest high torque servo commercially available (e.g., HS-35HD servo motor). Note that  FIG. 4A  shows such a shielding layer  232  placed in front of the latching magnet  218 B- 1 . The shielding layer  232  may be made flush with the front surface of the latching rotor  214 B. In one embodiment, the shielding layer  232  and the latching rotor may be made of the same material. In another embodiment, the shielding layer  232  is made integral with the latching rotor  214 B. However, it is possible to place the shielding layer  232  over the latching rotor or directly over the latching magnets. 
     In one embodiment, the robot shown in  FIG. 3  may be entirely, uniquely, designed and 3D printed with the components list illustrated in  FIG. 8 . This specific design includes the four side faces  210  and two stationary top and bottom faces  202 . As previously discussed, the robot  200  shown in  FIG. 3  is not capable of self-locomotion and hence, an external actuation platform  700  is used (see  FIG. 7A ) for its movement and interactions with other similar robots. Note that the magnetic latching mechanism  230  disclosed herein is completely self-assisting, i.e., it can pull the robots close as well as push them away depending on the latching rotor&#39;s orientation, which can be controlled by processor  204  and servo-motor  208 . To ensure reliability and consistency in bonding/de-bonding action, the latching rotor  214  has two mechanical braking arms  217 A along its diameter to avoid any over rotation that might be caused by a servo slip, for instance. 
     One or more of the advantages of the embodiments presented above is now discussed. The robot shown in  FIG. 3  may be scaled down to be a compact mechatronic design having dimensions of about 5×5×5 cm and a weight of only 95 g. The bond strength achieved between two robots  200  is high compared to EPMs of similar size (4×0.58 kg pull on attraction mode). 
     The experiments performed with the robot  200  reveal that for such a small mechanism, the forces required to dismantle the bond are impressive. The following peak values of the force tests were measured. For side face—side face attraction the measured force was 8.7 N. Note that no other robot of this size with EPMs has a stronger bond strength to the knowledge of the inventors. For side face—side face repulsion, the measured force was 6.9 N. Again, no other robot of this size with EPMs have a strength greater than this for bond break/repulsion. For side face-side face slide, the maximum measured force was 4.3 N. 
     The torque required to break the bond was measured to be 0.065 Nm. This is in accordance with the design of the robot, i.e., the placement of the latching magnets relative from the center of rotation of the latching rotor and the plastic shielding in between the contact faces. This value of torque is quite high given the small size of the mechanism. Also, the value of this torque is below the maximum allowed torque of the servo used (0.078 Nm), which makes it extremely reliable to use. 
     Three modes of operation are possible for the robot  200 : (1) attach (bond formation), (2) detach (bond breaking), and (3) repel (avoidance, which is achieved when the latching magnets of the two robots are aligned but have the same polarities facing each other). EPMs do not have this third mode, the repel mode. This avoidance feature is unique to the design shown in the figures and this feature removes the need of local communication between the neighboring robots. 
     The robot  200  discussed above consumes less power than an EPM (of comparable size/strength). This is so because there is no power used for bond formation, and there is little energy used for bond breaking. Each ultra-nano servo draws a peak current of 0.36 A at a rotation stall (which doesn&#39;t happen during normal operation) and the idle state current is 0.008 A, which is less on average than each of the EPMs that need a peak current&gt;1 A during activation or deactivation. Further, the robot uses zero power for avoidance, i.e., instantaneous repelling of other robots. 
     The robot  200  also has the capability of self-alignment of the faces and the contacts. There is no additional sensing or actuation force required for this feature, i.e., the bond formation and bond breaking are self-assisted. Two approaching robots can self-align their faces to make a bond or repel each other depending on the orientation of the face magnets. Also, the bond breaking is self-assisted. It does not only break the bond, but the generated repulsion force is enough to push two robots in opposite directions. 
     The magnetic latching mechanism discussed with regard to robot  200  is highly scalable, i.e., the same concept can be extended to bigger magnets and higher torque servos as well for bigger and stronger bonds in latching components. The joints can also be used for collective robots locomotion in future. Also, those skilled in the art would understand that the above discussed magnetic latching mechanism may be used not only with robots, but also with other devices, e.g., drones, cars, trains, planes, etc. The discussed magnetic latching mechanism may be used with various electrical components, home appliances or in various buildings for achieving the required docking or undocking of objects. 
     The disclosed embodiments provide methods and mechanisms for docking or bonding and undocking or unbonding two or more robots using a magnetic latching mechanism. It should be understood that this description is not intended to limit the invention. On the contrary, the embodiments are intended to cover alternatives, modifications and equivalents, which are included in the spirit and scope of the invention as defined by the appended claims. Further, in the detailed description of the embodiments, numerous specific details are set forth in order to provide a comprehensive understanding of the claimed invention. However, one skilled in the art would understand that various embodiments may be practiced without such specific details. 
     Although the features and elements of the present embodiments are described in the embodiments in particular combinations, each feature or element can be used alone without the other features and elements of the embodiments or in various combinations with or without other features and elements disclosed herein. 
     This written description uses examples of the subject matter disclosed to enable any person skilled in the art to practice the same, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the subject matter is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims.