Resolution you can recompute
21-bit absolute encoders resolve 2,097,152 positions per revolution — 0.618 arcseconds per increment, which is the same figure as 0.000171661 degrees and can be recomputed from the bit depth.
Real-time motion platform One node in your
control graph.
Robotics and industrial work judges a real-time motion platform on engineering tolerances rather than on how it feels. The Portal Development Kit (PDK) is a development kit judged on those terms.
Development Kit: early-access hardware, software in active development.
Four properties
What actually matters on a bench.
Backlash-free by architecture
Gear meshes and harmonic drives introduce play that compounds across cycles. There is no gearbox, belt or ballscrew here to introduce it. Its backlash is zero.
Transparent in real time
The platform is one node in a hardware-in-the-loop chain: game-to-motion commands in at 1 kHz.
No gearbox to wear
Direct drive has no gearboxes, oil or brushes, the transmission parts that wear on geared hardware.
Figures for the bench
The numbers behind the four properties.
| Quantity | Value | Basis |
|---|---|---|
| Drive loop, per motor | 8 kHz | ARK drive firmware |
| Control loop | 3.3 kHz | ARK control firmware |
| Game to motion | 1 kHz | ARK specification |
| Encoder positions per revolution | 2,097,152 | 21-bit absolute encoder on every motor: 2 to the 21st power |
| Motion bandwidth | 1 kHz | ARK specification |
| Vibration | up to 629 Hz | Measured on the rig with up to 250 kg on board; each motor reproduces up to 2,000 Hz |
| Payload | up to 250 kg | Rider, seat, cockpit and everything on the platform |
| Backlash | 0 | Direct drive: no gears between motor and leg |
| Out-of-envelope pose | refused | The inverse kinematics returns an error rather than clamping the pose |
For hardware-in-the-loop work the last row matters most: a pose outside the envelope is refused with an error your stack can log.
Development uses
Three benches this becomes.
Parallel-kinematics research
Inverse-kinematics solver validation and model-predictive control on the canonical Stewart-Gough architecture, with a documented machine underneath.
Sensor and perception validation
A controlled dynamic platform for IMU, camera and LiDAR development and ADAS bench work.
Calibration and alignment
Gimbal stabilization rigs and camera and optical-axis development work.
Integration
Commands
over a socket.
The platform accepts six-axis pose commands over UDP. There is no proprietary layer to adopt. If your work needs to sit below the pose interface, direct actuator mode gives you the six legs and the solver gets out of the way.
Keep reading
Closed-loop control
The three nested loops, and what closing a loop on the motor shaft does and does not tell you.
The Stewart platform
The geometry, and the three ways parallel kinematics is harder.
Talk to us
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