Patent Application
20120268045
The invention in general, relates t0 braking an electric motor, and more specifically, to a method and apparatus for braking an electric motor by substantially negating an instantaneous motor electromotive force generated by the electric motor.
Electric motors are used in a variety of applications, including machine tools, robotic arms, vehicles, earth movers, heavy-duty machines, trains, etc. Considering an example of an electric vehicle, an electric motor is a fundamental component of a power train of the electric vehicle. Among other functions, the electric motor is a source of power and torque.
The electric motor may be, for example operated to produce a positive torque for operating machines in a motoring mode. These machines may include braking mechanisms that may be used to generate frictional forces opposite to the direction of movement of parts of the machines for stopping the movement of these parts. However, these frictional forces generated may lead to wear and tear of the parts of the machines. For example, in order to decelerate a vehicle, the vehicle is equipped with one or more mechanisms in its power train that when operated are capable of applying a load on the power train. These mechanisms include wheel brakes that apply frictional forces to wheels during rotation, thus creating a torque that opposes rotation of the wheels. This torque creates forces at the interfaces between the wheels' tires and road surface opposing the direction of vehicle motion, thereby decelerating the vehicle. However, the frictional forces that act on the rotating wheels generate heat that raises brake temperature. The heat and wear created by applications of the brakes multiple times eventually degrade brake linings or brake pads, necessitating their replacement. Further, as a result of this degradation of the brake linings the deceleration of the vehicle tends to become ineffective. There may be a delay between an instant where brakes are applied and an instant where the vehicle is eventually stopped. This ineffective deceleration of the vehicle may be hazardous to pedestrians, thus causing many accidents.
Therefore, there is a need for a method and apparatus for braking an electric motor by substantially reflecting a polarity of an instantaneous motor electromotive force generated by the electric motor. Additionally there is a need for the braking of the electric motor to be frictionless.
The accompanying figures, where like reference numerals refer to identical or functionally similar elements throughout the separate views and which together with the detailed description below are incorporated in and form part of the specification, serve to further illustrate various embodiments and to explain various principles and advantages all in accordance with the invention.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the invention.
Before describing in detail embodiments that are in accordance with the invention, it should be observed that the embodiments reside primarily in combinations of method steps and apparatus for braking an electric motor by substantially reflecting a polarity of an instantaneous motor electromotive force generated by the electric motor. Accordingly, the apparatus components and method steps have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.
In this document, relational terms such as first and second, top and bottom, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms “comprises,” “comprising,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, or apparatus. An element proceeded by “comprises . . . a” does not, without more constraints, preclude the existence of additional identical elements in the process, method, or apparatus that comprises the element.
Various embodiments of the invention provide a method and apparatus for braking an electric motor. The apparatus includes an electric motor, an electric generator, and an electrical circuit arrangement capable of connecting the electric generator to the electric motor. The electric generator generates an instantaneous generator electromotive force at substantially equal magnitude and opposite polarity to an instantaneous motor electromotive force present in the electric motor. The electrical circuit arrangement is capable of supplying the instantaneous generator electromotive force to the electric motor. The instantaneous generator electromotive force is supplied in response to connecting the electric generator and the electric motor. The instantaneous generator electromotive force substantially negates the instantaneous motor electromotive force generated by the electric motor, thereby braking the electric motor.
Electric motor 105 receives power from a power source 120. In an embodiment, power source 120 may be an energy storage device. In another embodiment, power source 120 may be a direct power source. Power source 120 supplies the power to electric motor 105 through electrical circuit arrangement 115 by establishing a connection. In an embodiment, electrical circuit arrangement 115 may include one or more wires for transmitting power. For example, electrical circuit arrangement 115 includes two wires for supplying the power to electric motor 105. On supplying the power, a motor electromotive force present in electric motor 105 is measured. The motor electromotive force generated in electric motor 105 is an instantaneous motor electromotive force. The motor electromotive force generated needs to be negated to brake electric motor 105. For example, if the instantaneous motor electromotive force is E1 at time t1, an instantaneous electromotive force E2 at time t2 which is substantially equal in magnitude and opposite in polarity to the instantaneous motor electromotive force E1, is required to negate the instantaneous motor electromotive force E1. As the instantaneous electromotive force E2 is opposite in polarity to the instantaneous motor electromotive force E1, net electromotive force at electric motor 105 at time t2 is zero. Therefore, electric motor 105 is braked instantly i.e., at time t2 without generating friction caused from opposing the direction of rotation of electric motor 105.
To this end, apparatus 100 includes an electric generator 110 capable of generating an instantaneous generator electromotive force for negating the motor electromotive force generated by electric motor 105. The instantaneous generator electromotive force is generated at substantially equal in magnitude and opposite in polarity to the instantaneous motor electromotive force present in electric motor 105. The instantaneous generator electromotive force is generated at one or more output terminals of electric generator 110. Electric generator 110 produces electric current through electromagnetic induction. The electric current is then converted into the instantaneous generator electromotive force.
The instantaneous generator electromotive force is then supplied to electric generator 110 through electrical circuit arrangement 115 capable of connecting electric generator 110 and electric motor 105. Electrical circuit arrangement 115 connects one or more output terminals of electric generator 110 and one or more input terminals of electric motor 105. Thus, the instantaneous generator electromotive force generated at the one or more output terminals of electric generator 110 is supplied to one or more input terminals of electric motor 105. For example, one or more wires connecting the one or more output terminals such as, one or more pins of electric generator 110 transmit the instantaneous generator electromotive force to the one or more input terminals of electric motor 105. This instantaneous generator electromotive force negates the motor electromotive force to brake electric motor 105.
In an embodiment, the instantaneous generator electromotive force may be supplied in response to establishing a connection between electric generator 110 and electric motor 105. Apparatus 100 includes a switch, such as a switch 125 for establishing the connection between electric generator 110 and electric motor 105. Once the connection is established, electrical circuit arrangement 115 is completed. The connection between electric generator 110 and electric motor 105 may be established on actuation of switch 125.
In an embodiment, electrical circuit arrangement 115 is capable of processing the instantaneous generator electromotive force prior to supplying the instantaneous generator electromotive force to electric motor 105. For example, the instantaneous generator electromotive force generated at electric generator 110, such as E3 may lose magnitude due to frictional losses or due to any other losses experienced within electric motor 105. The instantaneous generator electromotive force E3 is equal to the instantaneous electromotive force E2 mentioned in the previous example. Therefore, the instantaneous generator electromotive force E3 may be reduced by a reduction component “x”, to E3−X. In this scenario, the instantaneous generator electromotive force E3 may not be substantially equal in magnitude to the instantaneous motor electromotive force present in electric motor 105, such as E1.However, it will be readily apparent to a person of ordinary skill in the art that the reduction component “x” may be negligible in magnitude.
In cases where the instantaneous generator electromotive force is reduced, electrical circuit arrangement 115 processes the instantaneous generator electromotive force to be substantially equal in magnitude to the instantaneous motor electromotive force present in electric motor 105. More specifically, the reduced instantaneous generator electromotive force E3−x is then stepped up to the instantaneous generator electromotive force E3 which is substantially equal in magnitude and opposite in polarity to the instantaneous motor electromotive force E1. It will be apparent to a person skilled in the art that the reduced instantaneous generator electromotive force is stepped up using any electrical unit known in the art.
Therefore, the instantaneous generator electromotive force substantially negates the instantaneous motor electromotive force generated by electric motor 105. Consequently, electric motor 105 is braked instantly without generating friction caused by opposing the direction of rotation of electric motor 105. Apparatus 100 may be implemented in one or more of machine tools, robots, vehicles, earth movers, and heavy-duty machines, trains for instant braking without friction. In vehicles and trains, apparatus 100 may be implemented during emergency situations, such as to prevent accidents.
In an embodiment, electric motor 105 is connected to one or more moving members through a shaft (not numbered in
Explaining by way of an example, apparatus 100 is implemented in robotic arms for instantly braking movement of the robotic arms without friction. An electric motor driving a robotic arm receives power from a power source via an electrical circuit arrangement. On receiving the power, a motor electromotive force present in the electric motor is measured. The motor electromotive force generated in the electric motor is an instantaneous motor electromotive force. The instantaneous motor electromotive force needs to be reflected to brake the electric motor. Apparatus 100 includes an electric generator for generating an instantaneous generator electromotive force at substantially equal in magnitude and opposite in polarity to the instantaneous motor electromotive force present in the electric motor. This instantaneous generator electromotive force substantially negates the instantaneous motor electromotive force generated by the electric motor. Thus, the substantial reflection of the instantaneous motor electromotive force instantly brakes the movement of the robotic arm without friction.
In another example, apparatus 100 is implemented in a vehicle for rapidly braking movement of the vehicle. An electric motor is used to drive the one or more wheels. The electric motor receives power from a power source via an electrical circuit arrangement. On receiving the power, a motor electromotive force present in the electric motor is measured. The motor electromotive force generated in the electric motor is an instantaneous motor electromotive force. The instantaneous motor electromotive force needs to be negated to brake the electric motor. This is achieved using an electric generator. The electric generator generates an instantaneous generator electromotive force at substantially equal in magnitude and opposite in polarity to the instantaneous motor electromotive force present in the electric motor. This instantaneous generator electromotive force substantially negates the instantaneous motor electromotive force. Thus, the vehicle is rapidly stopped. For example, when a pedestrian or an animal suddenly crosses a path of the vehicle, apparatus 100 may be implemented in the vehicle for rapidly braking the movement of the vehicle, thereby preventing an accident during such emergency situations. The braking of the movement of the vehicle is explained in detail in conjunction with
Moving now to
Electric generator 210 is capable of generating an instantaneous generator electromotive force. The instantaneous generator electromotive force is generated at substantially equal in magnitude and opposite in polarity to the instantaneous motor electromotive force. The instantaneous generator electromotive force is generated at one or more output terminals of electric generator 210. It would be readily apparent to a person of ordinary skill in the art that electric generator 210 may be positioned anywhere within system 200.
Electrical circuit arrangement 215 is capable of connecting electric generator 210 to electric motor 205. The instantaneouss generator electromotive force generated at the one or more output terminals of electric generator 210 is supplied to one or more input terminals of electric motor 205. The instantaneous generator electromotive force is supplied in response to connecting electric generator 210 and electric motor 205. In an embodiment, a connection between electric generator 210 and electric motor 205 may be established in response to actuation of a switch, such as a switch 235. More specifically, electrical circuit arrangement 215 connects electric generator 210 and electric motor 205 when switch 235 is actuated. Thereafter, the instantaneous generator electromotive force is supplied to electric motor 205 to substantially negate the instantaneous motor electromotive force. As a result, one or more wheels 220-n stop instantly without generating friction caused by opposing the direction of rotation of one or more wheels 220-n.
In an embodiment, electrical circuit arrangement 215 may be capable of processing the instantaneous generator electromotive force prior to supplying the instantaneous generator electromotive force to electric motor 205. This is performed because there may be loss in magnitude of the instantaneous generator electromotive force due to frictional losses or due to any other losses experienced within electric motor 105. This is explained in conjunction with
In an embodiment, a vehicle may include one or more systems similar to system 200. Each system may include an electric motor, an electric generator, and an electrical circuit arrangement. For example, a system such as, system 200 may be connected to each wheel of a car. In this case, an electric motor may be connected to each wheel of the four wheels of the car. In an embodiment, single electric generator may supply an instantaneous generator electromotive force to each electric motor for braking the wheels. Alternatively, a system may include four generators. Each generator may supply instantaneous generator electromotive force to a motor connected to a corresponding wheel of the car for stopping the car.
In this embodiment as described in
Electric generator 310 is capable of generating an instantaneous generator electromotive force. The instantaneous generator electromotive force is generated at substantially equal in magnitude and opposite in polarity to the instantaneous motor electromotive force present in electric motor 305. In this embodiment, electric generator 310 is driven directly by electric motor 305. Electric motor 305 may be connected to a first end of axle 325 of the electric vehicle, whereas electric generator 310 may be connected to a second end of axle 325. Therefore, electric generator 310 rotates at an angular velocity that is equal to an angular velocity of electric motor 305. The rotation of electric generator 310 at an angular velocity equal to the angular velocity of rotation of electric motor 305 allows electric generator 310 to generate the instantaneous generator electromotive force. This similarity of angular velocity results in generation of the instantaneous generator electromotive force at substantially equal in magnitude and opposite in polarity to the instantaneous motor electromotive force present in electric motor 305.
In an alternative embodiment, electric generator 310 may be placed above electric motor 305. Thus, the rotational torque produced by electric motor 305 may be transmitted to electric generator 310 using any transmission transferring arrangement. The transmission transferring arrangement, may be for example, but not limited to a gear arrangement and a pulley arrangement.
The instantaneous generator electromotive force generated by electric generator 310 is then supplied to electric motor 305 via electrical circuit arrangement 315. The instantaneous generator electromotive force is supplied when a connection is established between electric generator 310 and electric motor 305 using electrical circuit arrangement 315. In an embodiment, the connection may be established by actuating a switch, such as a switch 335. This is explained in conjunction with
In an embodiment, electrical circuit arrangement 315 is capable of processing the instantaneous generator electromotive force prior to supplying the instantaneous generator electromotive force to electric motor 305. For example, the instantaneous generator electromotive force generated at electric generator 310 may lose magnitude due to frictional losses. Therefore, the instantaneous generator electromotive force may not be substantially equal in magnitude to the instantaneous motor electromotive force. In such cases, electrical circuit arrangement 315 processes the instantaneous generator electromotive force to be substantially equal in magnitude to the instantaneous motor electromotive force present in electric motor 305. The reduced instantaneous generator electromotive force is then stepped up to the instantaneous generator electromotive force, which is substantially equal in magnitude and opposite in polarity to the instantaneous motor electromotive force. This is explained in conjunction with
Thereafter, at step 404 the instantaneous generator electromotive force is supplied to the electric motor via an electrical circuit arrangement by establishing a connection. The instantaneous generator electromotive force generated at the one or more output terminals of the electric generator is supplied to one or more input terminals of the electric motor. The process of supplying the instantaneous generator electromotive force is described in conjunction with
Various embodiments of the invention provide a method and apparatus for braking an electric motor. The apparatus includes an electric motor, an electric generator, and an electrical circuit arrangement capable of connecting the electric generator to the electric motor. The electric generator generates an instantaneous generator electromotive force at substantially equal magnitude and opposite polarity to an instantaneous motor electromotive force present in the electric motor. Therefore, the instantaneous generator electromotive force brakes the electric motor instantly without generating friction caused from opposing the direction of rotation of the electric motor. The apparatus may be implemented in one or more of machine tools, robotic arms, hybrid electric vehicles, earth movers, heavy-duty machines, and trains. for instant braking without friction.
Those skilled in the art will realize that the above recognized advantages and other advantages described herein are merely exemplary and are not meant to be a complete rendering of all of the advantages of the various embodiments of the present invention.
In the foregoing specification, specific embodiments of the invention have been described. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the invention as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of the invention. The benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential features or elements of any or all the claims. The invention is defined solely by the appended claims including any amendments made during the pendency of this application and all equivalents of those claims as issued.
