Single Axis Rate Table
The single axis table was the result of a developed under Ministry of Defence sponsorship. The spindle is designed to have very high resonant frequencies between motor and load and between motor and tachogenerator. This allows for a higher servo bandwidth frequency and therefore very low ripple with very high accuracy.
Smaller ball angular contact ABEC 9 grade bearings are used on all standard tables (air bearings are used for ultimate precision tables). Each bearing is individually measured and are mounted using a custom tolerances. These custom tolerances are required in order to produce the required low levels of wobble and friction over the life of the system. The tables produce a wobble better than 1 arc second and has axial and radial error motion better than 0.5 micron and 2.5 micron respectively
These performance characteristics are maintained over a wide range of operating temperatures by using customized wave- spring washers to maintain the required level of bearing preload.
In order to achieve the highest possible system bandwidth, the motor is mounted as closely as possible to and between the platen (load) and the tachogenerator/encoder. With the motor close proximity to the tachogenerator it is necessary to take measures to prevent magnetic coupling pickup at the tachogenerator when the motor is energised. The table is mounted in an aluminium housing, spindles are non-magnetic stainless steel and to remove residual airborne magnetic coupling, a 'Mu-metal' shield is fitted in the air gap between the motor and tachogenerator rotors.
In order to achieve the required 0.1 percent torque ripple and linearity, the tachogenerator is during manufacture by optimising the position of the commutation relative to the poles of the permanent magnet stator.
Single axis rate table specifications:
- Motor torque range: 11Nm to 110Nm
- Max speed range: 1000 °/s to 3000 °/s
- Speed resolution range: 0.001 °/s to 0.0001 °/s
- Rate accuracy range: 0.1% to 0.01%
- Position accuracy range: +/-3.6 arc sec to +/-1 arc sec
- Platen size range: 12” to 24”
- Load capacity: 200kg
- Axial error motion (max): 0.0005mm
- Radial error motion (max): 0.001mm
- Wobble (max): 1 arc sec
High Speed Table specication
These tables have air-cooled, brushless motor drives, with digital tachogenerator feedback from a high speed optical encoder, and dynamically balanced rotors, to achieve operating speeds up to l0,000 rpm (60,000deg/sec).
- Motor Torque: 9.5Nm
- Load Capacity: 5kg
- Platen diameter: 150mm
- Max Speed: 60000 °/s
- Min speed: 500 °/s
- Rate control accuracy: 1x10-5
- Rate measurement accuracy: 1x10-5
High speed, low noise slip rings are available to power and monitor devices under test.