(spring 2001)

  

Baps is a 3D ballistic walking robot, efficiently stabilized by limit cycle control. Results with an effective limit cycle controller have led to minimal results. Read about it in the Delft Outlook article. It seems that Baps performs best when in "open loop" mode (without control) as shown in the videos at the end of this page.

Baps is an improvement of Stappo on the following aspects:

1. increasing the step length
2. increasing stability
3. decreasing the power consumption
4. pneumatic activation by McKibben muscles

In total six McKibben muscles sustain and control the oscillatory walking motion. A DSP-board controls the valves to the muscles.

   

One of the important conclusions from our experiments with Baps is that it is not correct to assume that the lateral motion is decoupled from the sagittal motion. We apply this knowledge in our next prototype (MIKE) by taking a step back and concentrating on the sagittal motion. Sideways stability remains unsolved for now.

Actuation

For the actuation of Baps we use pneumatically driven McKibben muscles. To achieve full autonomy, we are developing miniaturized pneumatics.

    

 

  

 

 

For autonomous function the biped needs pneumatic logic like pressure regulators, valves, and supply. In order to keep the energy consumption minimal, low power valves and leak-free pressure regulators are needed. Because of the field of application the weight and space for the required pneumatics must be kept as low as possible. Commercially available pneumatics do not fulfill these requirements. Based on the available experience of the Wilmer group in developing miniature pneumatics for pneumatically powered prostheses and orthoses, see for example: Myopneumatic hand for children, we are developing our own special miniature pneumatics for the biped.

 

Simulations

In order to optimize the robot design, and muscle activation pattern the parameter space of simulated walking cycles was studied. Periodic walking cycles were found by applying Poincaré´s return map analysis. Four simulation results are given as mpeg-movies. Movie 1 shows a simulation of a passive walker with an active compliant stance leg. Because the stance leg stiffness is too low a large hip displacement in mid stance is the result. Making the stance leg stiffness larger in combination with a critical stance leg damping (to prevent hip oscillations) walking with a smooth hip trajectory is obtained, shown in Movie 2. Nice to see is the existence of a funny walking pattern like in Movie 3 (I call it cool walking), obtained by a rather critical ratio of damping, stiffness and body weight. Adding hip active stiffness to compensate for energy losses in the hip joint, a walking pattern like Movie 4 is obtained.

     

 

  

Movies

This movie shows Baps walking in "open loop" mode (without control):