Abstract:
A system for active control of noise and/or vibration includes an electric machine; at least one sensor for sensing at least one of noise and vibration in the machine and generating at least one of an audio signal representing noise and a vibration signal representing vibration; a controller obtaining at least one of the noise signal and the vibration signal, the controller generating control signals to reduce at least one of noise and vibration in the machine; and power electronics receiving the control signals and generating drive signals for the machine.

Description:
BACKGROUND OF THE INVENTION 
     The subject matter disclosed herein relates to control systems and, more particularly, to a method and system for active noise and/or vibration control of systems such as an elevator system. 
     Elevators use a machine (e.g., electric motor and traction sheave) to drive belts or ropes coupled to elevator cars. The machines have structures (e.g., frames) that are designed to meet strength requirements first, leaving noise and vibration to a lesser priority. Noise and/or vibration in the machine can be sensed by occupants of the elevator car, thereby degrading the experience of traveling in the elevator. There is a need in the art for methods and systems for reducing noise and/or vibration in elevator systems. 
     BRIEF DESCRIPTION OF THE INVENTION 
     According to one aspect of the invention, a system for active control of noise and/or vibration includes an electric machine; at least one sensor for sensing at least one of noise and vibration in the machine and generating at least one of a noise signal representing noise and a vibration signal representing vibration; a controller obtaining at least one of the noise signal and the vibration signal, the controller generating control signals to reduce at least one of noise and vibration in the machine; and power electronics receiving the control signals and generating drive signals for the machine. 
     According to another aspect of the invention, a method for active control of noise and/or vibration in a system includes sensing at least one of noise and vibration at an electric machine to generate at least one of a noise signal and a vibration signal; generating control signals to reduce at least one of noise or vibration in the machine in response to at least one of the noise signal and the vibration signal; and generating drive signals for the machine in response to the control signals. 
     These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a block diagram of an elevator system; and 
         FIG. 2  is a flowchart of a process for active noise and/or vibration control. 
     
    
    
     The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings. 
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is a block diagram of various components of an elevator system  100  in exemplary embodiments. Components of the system  100  not required for an understanding of the present invention (e.g. guide rails, safeties, etc.) are not discussed below. System  100  includes two components, namely electric machine  102  and drive  104 . Machine  102  imparts motion to the elevator car (not shown) and includes a motor  106  and a traction sheave  108 . Motor  106  may be a brushless, permanent magnetic electric motor. In response to drive signals from drive  104 , motor  106  turns the traction sheave  108 . Rope(s) or belt(s) (not shown) are looped over traction sheave  108  and are coupled to the elevator car as known in the field. Motor  106  and traction sheave  108  may be mounted on a bedplate  110 . 
     Drive  104  includes a controller  120  and power electronics  122 . Controller  120  may be implemented using a general-purpose microprocessor executing computer program instructions stored in a computer readable storage medium. In alternate embodiments, controller  120  may be implemented in a peripheral integrated circuit element, a CSIC, ASIC or other integrated circuit, a logic circuit, a digital signal processor, a programmable logic device such as a FPGA, PLD, PLA or PAL, or any other device or arrangement of devices that is capable of implementing processes. Controller  120  is programmed to implement the functions described herein. As described in further detail herein, controller  120  generates control signals to compensate for noise and/or vibration in machine  102 . Although shown in  FIG. 1  as being adjacent the machine  102 , drive  104  could be located at any suitable location. 
     Power electronics  122  receive control signals from the controller  120  and generate drive signals to the motor  106 . The drive signals from power electronics  122 , as a primary function, dictate the direction and speed of motor  106  to operate the elevator car through multiple modes. In present invention, the drive signals additionally serve to reduce noise and/or vibration by using the motor  106  as an actuator to generate specific vibrations to cancel noise-radiating vibrations of the machine  102  and therefore reduce noise radiation. 
     One or more sensors are employed around the machine  102  to gather information used by controller  120 . One or more accelerometer or vibration sensors  130  may be mounted to a surface subject to vibration such as the bedplate  110  or motor  106  to detect structure-borne noise or vibration. An audio sensor (e.g., microphone)  132  may be mounted near the machine  102  to detect acoustic noise emanating from the machine  102 . A speed sensor  134  (e.g., rotary encoder) detects the speed of the motor  106  and traction sheave  108 . The speed sensor  134  may be mounted to a motor shaft or the traction sheave. In alternate embodiments, the speed of motor  106  is derived from the control signals issued by controller  120 , eliminating the need for the speed sensor  134 . 
       FIG. 2  is a flowchart of exemplary processing implemented by the controller  120 . The process begins at  200  where the machine is operated in typical fashion. In other words, the drive  104  controls the speed and direction of motor  106  in response to elevator calls and normal elevator operational states. At  202 , controller  120  obtains a vibration signal from vibration sensor  130 . At  204 , controller  120  obtains a noise signal from audio sensor  132 . At  206 , controller  120  obtains a speed value, which may be derived from speed sensor  134  or derived internally by controller  120  based on control signals generated by controller  120 . 
     At  208 , controller  120  uses one or more of the speed value, the noise signal and the vibration signal to derive the control signals applied to the power electronics  122 . The control signals include an operational component that dictates the motor speed and direction in response to elevator car requirements. The control signals also include a correction component to address noise and/or vibration detected by the audio sensor  132  and/or the vibration sensor  130 . Controller  120  operates as part of a control loop to reduce spectral components of noise and/or vibration in the machine  102 . The control algorithms in the controller  120  provide stable operation of the machine  102 . 
     Controller  120  may filter the noise signal and/or vibration signal to target certain frequencies. Target frequencies may correspond to expected mechanical resonances from components of the machine  102 . Other target frequencies may correspond to an electromagnetic (EM) harmonic (e.g., equal to or higher than the 6 th  harmonic) from the machine  102 . Adaptive control algorithms may be used to generate control signals to dampen vibration and/or noise in machine  102 . 
     The power electronics  122  generate drive signals for motor  106  in response to the control signals from controller  120 . The drive signals from power electronics  122  operate motor  106  as an actuator to control vibrations of the machine  102 . The correction component of the control signals are incorporated in the drive signals to use the motor  106  to dampen vibration and/or noise sensed in the machine  102 . Accordingly, the machine  102  continues to impart motion to the elevator car as intended, but also includes corrective forces to reduce or modify vibrations and/or noise in the machine  102  to improve user experience in the elevator car or in an adjacent room to the machine. 
     While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.