Fully flexure-based precision hexapod

T-Flex: Fully flexure-based precision Hexapod

  • 6 DOF with large range of motion
  • Parallel kinematic structure for low moving mass and large accelerations 
  • Fully flexure-based joints for high repeatability 
    (no backlash, low hysteresis, no wear, no contamination)
  • Direct drive iron-core rotary motors (back-drivable, no backlash, no contamination)
  • H2 feedback control to optimally reject amplifier's current noise

Movie of the first motion of the T-Flex on Sept 6 2019. The amplifier current is limited to about 10% of the maximum. The controller is a SISO preliminary PID type without feedforward.  


Movie of the T-Flex with the controller set to supply a constant drive force to statically obtain the neutral platform position. Note the low natural frequency and damping in the degrees of freedom. The internal vibration mode frequencies (mode 7 and higher) are about a factor of 30 higher than the ones in the degrees of freedom. The damping is mainly originating from the torque motor and its driver.    

Specifications

Dimensions: 650x650x400 mm 
Translational workspace: 5L with inner cube of 100x100x100mm
Translational travel range* x, y, z (with z the vertical axis): +/-100mm (100mm bidirectional)
Rotational travel range* Rx, Ry, Rz (with z the vertical axis): +/-15 degrees (15 degrees bidirectional)
  *The travel range given is the maximum travel, where all other axis remain at their zero (neutral) position

Repeatability: 50nm (expected with fully metal flexures)
Load capacity: 10kg (with fully metal flexures)
Acceleration: 5-10g (small payloads)

Flexure-based high -torque iron-core motor suspension testing

This video shows the modified butterfly hinge design of the iron-core motor suspension with the slaving mechanism. The low hysteresis of the flexure-based design is demonstrated.  

This video shows some initial controller tests of the high-torque direct-drive motor with the flexure-based suspension. 

Scientists involved

M. Naves, M. Nijenhuis, M.D. Plettenburg, D.W. Vogel, R.G.K.M. Aarts, W.B.J. Hakvoort, D.M. Brouwer

Related publications

Naves, M., Aarts, R. G. K. M., & Brouwer, D. M. (2019) Large stroke high off-axis stiffness three degree of freedom spherical flexure joint, Precision engineering, Volume 56, pp. 422-431. https://doi.org/10.1016/j.precisioneng.2019.01.011.

M. Naves, D.M. Brouwer, R.G.K.M. Aarts, Building block based spatial topology synthesis method for large stroke flexure hinges, ASME robotics and mechanisms, 2017, doi: 10.1115/1.4036223.

Acknowledgement

This research was part of the VIDI project 'Large range of motion spatial flexure joints', a personal grant of Dannis Brouwer, funded by the Innovative Research Incentives Scheme VIDI (14152 NWO TTW Toegepaste Technische Wetenschappen) of the Ministry of Education, Culture and Science of the Netherlands.