Mechanical vibration can be extremely problematic within applications requiring abrupt stopping and/or starting. For example, gantries typically require such movement, as a gantry beam is employed to position a tool over a particular surface. As applications have required length of the gantry beams to increase, amplitude of mechanical vibration upon the gantry beams (and thus the tool) likewise increases. Because various applications (e.g., surface monitoring of large flat-panel television screens) presently require beams of considerable length, mechanical vibration occurring during operation of the gantry (e.g., abrupt stopping and/or starting) can become substantial on the gantry beam. Such mechanical vibration can result in damage to the tool as well as decreased application efficiency, as the application must be delayed until the mechanical vibration has settled. If the application continues while a large amount of mechanical vibration remains, quality of the application will be compromised and the tool can suffer considerable damage. Similarly, other moveable machinery/equipment and/or machinery/equipment that facilitates movement such as conveyors, motors, pumps, chucks, rails, generators, tracks, chucks, housings, platforms, and various other vibration sensitive devices can be subject to unwanted mechanical vibration due to such movement.
Monitoring acceleration, velocity, and deceleration of a gantry beam as it moves along a stationary frame, and comparing vibration corresponding to such parameters to determine optimal operation of the gantry given a particular application is one conventional method for limiting vibration (e.g., a maximum acceleration, velocity and/or deceleration of a gantry beam that results in an allowable amount of vibration is determined). Such a method, however, does not allow gantry applications to be completed with optimal efficiency, and throughput is negatively affected. Various feedback systems have also been used in an attempt to reduce mechanical vibration associated with gantry arms and/or beams as well as other moveable machinery/equipment. For example, position and overshoot of a gantry beam can be determined via joint sensors, and such position and overshoot can be fed back to a control system. The control system thereafter directs drive motors to apply a counterforce, thereby damping vibration resulting from starting and/or stopping the gantry beam. Such systems typically are subject to significant wear and are expensive, and are furthermore often ineffective, as response of the drive motors is not sufficient to control transient overshoot vibration.
Passive damping mechanisms, including washers, pads, and other forms of mounts to facilitate reduction of high and low resonance frequency vibrations, have also been utilized in connection with damping resonance resulting from stopping and/or starting machinery such as a gantry beam. Such mechanisms are simple and inexpensive, but are unable to adjust to changing needs of an application.
Increased capabilities and decreased cost of linear motors further renders conventional methods insufficient for damping mechanical vibrations associated with gantry beams driven by such linear motors. For example, velocity of a linear motor is currently limited only by available bus voltage and speed of control electronics. Furthermore, response rate of a linear motor driven device can be over 100 times that of a mechanical transmission, resulting in faster accelerations and settling times. Because extensions from gantries have become greater in length (e.g., gantry beams employed within a gantry), and current applications require sensitive positioning (e.g., optical scanning of flat-panel televisions on a micron level), there exists a strong need in the art for a system and/or methodology that facilitates improved damping of mechanical vibration associated with gantry operations.
USPTO Backgrounds
USPTO Backgrounds