Equipment Solutions offers many standard, off-the-shelf, linear voice coil stages. These stages can be quickly catagorized by a few key parameters including the aperture size if it has one, the range of motion, the motors force constant, how the motors rotor is guided and finally the type of position sensor.
Low Moving Mass Nearly all Equipment Solutions stages use a voice coil motor architecture. For applications requiring less than 50 millimeters of high speed motion a voice coil is ideal. Having a single phase winding the voice coil motor is much lighter than its longer stroke three phase bretheren. Making the moving mass smaller produces higher accelerations and average speed for a given input current.
To further reduce the moving mass some Equipment Solutions stages use flexure bearings, one of the lightest bearing technologies available. Togethher, the combination forms one of the most highly efficient translation stages available today.
Stiction & Friction Free Flexure Guidance Several Equipment Solutions stages use a flexure bearing to guide the moving coil and the user load. A flexure bearing is a bearing that allows motion by bending a load element. Flexure bearings have none of the troublesome stiction or friction found in a typical ball or roller bearing stages. Void of those effects, stage positioning is both more precise and more stable. With no friction or stiction to contend with step-and-settle speeds are allowed to approach noise free theoretical limits. Balanced Load Equipment Solutions Voice Coil Stages are all designed to place the users load directly over the force axis. Placing the load in this position will eliminate the possibility of tipping or tilting the load during accelerations. It also prevents other components in the motion train from ringing and negatively affecting servo stability and characteristics like step-and-settle times. Compact Design Since a voice coil motor has only a single phase or winding it is inherenitly smaller than any three phase motor.
Many Equipment Solutions stages use a flexure bearing for coil and load guidance. Use of a flexure bearing will yield the smallest motion axis fottprint when compared to any other bearing thechnology including ball and rollers.
High Resolution Position Sensor All standard stages from Equipment Solutions include a high-resolution, non-contact, electro-optic analog position sensor. Becuase this sensor is analog, it is noise limited. With standard noice filtering this sensor can repeatably report a stage position to within 200 nanometers. Product Name
( mm )
( mm )
( lbs )
LFA-1205 Linear Focus Actuator 12 5 Flexure Analog LFA-2010 Linear Focus Actuator 20 10 0.6 Flexure Digital /
LFA-3404 Linear Focus Actuator 34 4 2.0 Flexure Analog VCS-1010 Voice Coil Stage 10 10 0.6 X-Roller Digital /
VCS-2020 Voice Coil Stage 20 20 1.6 X-Roller Analog PVS-5.5 Parallelogram Voice
5 5 0.25 Flexure Analog SMS-12 Stepper Motor Stage 0 12 NA X-Roller Digital Custom Voice Coil Stages Varies Varies Varies Varies Varies
Equipment Solutions produces motorized linear stages that can be sub divided into two main catagories based on the motion guidance technology they use. This section is provided to help highlight the unique advantages of each.
Roller or Ball Bearings Flexures High Cross-Axis Stiffness: When compared to flexures, bearings provide a means to more rigidly couple the stage to its reference frame. That coupling makes the servo more immune from external perturbations such as vibration and oscillating loads induced by offset loads that generate torques. Under such extreme conditions system performance can exceed that normally achieved by systems using flexures. Light Weight: When contrasted to most other guidance systems including bearings, flexures are significantly lighter. Being lighter allows more of the motors force to be converted to acceleration. That higher acceleration can then translate into higher peak velocities. It can also allow the servo to operate at a higher bandwidth that in turn can improve position repeatability and settling time performance. Motion Purity: A bearing stage will only deviate from from its straight line motion by an amount described by the tolerances of the bearings themselves. By contrast, a flexure stage will almost always have at least one orthogonal axis where some parasitic motion is imparted into. Infinite Life: When designed correctly, flexures can bend a prescribed amount without fatigue. This is in direct contrast to roller or ball bearings which rely on friction, all be it rolling, to define the motion path. That friction directly translates to wear which in turn describes the finite life available from the bearing. Small repetitive motions are well known to accelerate the failure time of ball or roller bearings. When high accelerations are included, which can cause the ball or roller to slip or skid, it will cause life estimates to be significantly lowered. Under conditions such as this, that include short repetitive motions and high accelerations, a flexure design should be prominently considered. Friction Free Motion: By nature a flexure design does not include any friction or stiction. That lack of force non-linearities allows the system to control positioning with much higher resolution.