TUlip is a bipedal robot realized by Eindhoven/Delft/Twente university. The hardware is reasonably well documented, so it may serve as a starting point for our own design.

The robot has 6 DoFs per leg: a 3 DoF hip, a 1 DoF knee and a 2 DoF ankle. Ankle roll is passive, the other 5 DoFs are actuated.

Simulator

Data for simulating TUlip in the Gazebo simulator is available at http://wiki.ros.org/Robots/TUlip. This includes masses, moments of inertia, joint positions, etc.

Construction

A reasonably detailed drawing of the leg appears in [1]. As mentioned above, the ankle roll DoF is passive; ankle pitch and knee pitch are actuated by Bowden cables. The lower leg therefore contains no motors (only encoders).

The active lower leg DoF employ "series elastic actuation", i.e. there is a spring in series with the Bowden cable. [1] provides phase/magnitude plots of the effect of this.

The construction of the hip joint is described in [2]. The three hip DoF appear to be connected directly to the gears (no series elastic element).

Hi-res photo of the robot.

Motors

According to [1], TUlip uses (brushed) Maxon RE30 motors. (We assume they use the 36V version, but this does not make a large difference.) The datasheet lists the motor properties as follows:

  • Nominal speed: 7810 rpm (= 818 rad/s)
  • Nominal torque: 83.4 mNm
  • Stall torque: 936 mNm

[1] gives the bandwidth of the torque controller as 5-10 Hz.

The following table lists the reduction ratios of the various joints (from [1]; probably realized by planetary gears) and the resulting nominal speeds, nominal torques and stall torques (assuming ideal gears).

Joint Power [W] Reduction Nom. speed [rad/s] Nom. torque [Nm] Stall torque [Nm]
Ankle roll 0 n/a (passive) n/a n/a n/a
Ankle pitch 60 129 6.3 10.8 121
Knee pitch 60 155 5.3 12.9 145
Hip roll 60 111 7.4 9.3 104
Hip pitch 60 222 3.7 18.5 208
Hip yaw 60 86 9.5 7.2 80

References