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Hardware development on quadruped robots FINAL presentation

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1 Hardware development on quadruped robots FINAL presentation
Welcome to my final presentation of my semester project about hardware development on quadruped robots. Hardware development on quadruped robots FINAL presentation Andreas GASSNER 2nd Semester Master Microengineering Professor: Auke Jan IJSPEERT Supervisors: Alexander SPRÖWITZ Rico MÖCKEL November 11, 2018

2 Here you can see the outline of my presentation.
I will start with explaining the motivation of this project, then, I will give a short introduction of the hardware of the oncilla project. Further on i will present my thre main tasks of this semester. I will explain them in detail and each part, the RC servo motor debugging and the walkway will be finished by a conclusion. For your orientation i added the outline at the left side of each slide. Outline Motivation Oncilla project - Hardware Tasks of this semester project RC servo motor debugging Layout Implemented CPG Tests Analysis of the results Conclusion Walkway Walkway / Kistler force plate Different configurations Variants / Steel plates Final design 11/11/2018 Andreas Gassner

3 The motivation of this project is, as it is described in the review of Professor Ijspeert, the interaction between robotics and neurobiology including not only robots benefiting of locomotion models but also the validation of biological models on robots. To achieve this goal two quadruped robots are build. This allows us to test different CPGs behaviour, gait transistions, leg ratios and feedback implementation not only in simulations but also on real robots. Motivation Motivation Oncilla project Tasks of the project RC servo motor debugging Layout Implemented CPG Tests Analysis Conclusion Experimental setup Walkway / Kistler Diff. configurations Variants/Steel plates Final design 1 Central pattern generators for locomotion control in animals and robots: a review, IJSPEERT, Auke Jan, in Neural Networks, Vol 21/4, 2008 11/11/2018 Andreas Gassner

4 Oncilla project - Hardware
The oncilla project where Alexander Spröwitz is working on is part of the european amarsi project. In the Biorob 2 quadruped robot will be built, a small quadruped robot and a large oncilla robot. The small robot is based on the Cheetah platform. It serves as a quick test platform and has 2 RC servo motors per leg. The large oncilla has 2 bushless dc motors and 1 RC servo motor per leg. Finally a Central Pattern Generator with sensor feedback will be implemented on both robots. The simulations of the robots are then testet on a walkway. Oncilla project - Hardware Motivation Oncilla project Tasks of the project RC servo motor debugging Layout Implemented CPG Tests Analysis Conclusion Experimental setup Walkway / Kistler Diff. configurations Variants/Steel plates Final design 2 quadruped robots Small quadruped robot Based on the Cheetah platform 1 Quick test platform 2 RC servo motors per leg Large Oncilla 2 BLDC Motors per leg 1 RC servo motor per leg CPG with sensor feedback Walkway for testing and validation of simulations 2 3 1 Cheetah - compliant quadruped robot, RUTHISHAUSER Simon, 2008 2 Image from: 3 Image provided by Alexander Spröwitz 11/11/2018 Andreas Gassner

5 tasks of this semester project
My work is a subproject of the oncilla project. My three main tasks were the implementation and characterization of a CPG first in Matlab and then in C#. Secondly the debugging and initialization of a off-the-shelf RC servo motor control board. Where the CPG has then run through. Finally a completly different task but also linked to the project is the dseign of a walkway not only for quadruped but also for biped robots or the Amphibot and the implementation of the kistler force plate. In the next few minutes i will detail those tasks, where the first two tasks are strongly linked together. tasks of this semester project Implementation of a CPG Simulation in Matlab Transferred to C# Debug and initialize RC servo motor control board Pololu Mini Maestro 24 Run CPG through board Design of a walkway Quadruped, biped robots & AmphiBot Kistler force plate Motivation Oncilla project Tasks of the project RC servo motor debugging Layout Implemented CPG Tests Analysis Conclusion Experimental setup Walkway / Kistler Diff. configurations Variants/Steel plates Final design 1 2 11/11/2018 1 Online trajectory generation in an amphibious snake robot using a lamprey-like central pattern generator model, IJSPEERT, Auke Jan and CRESPI, Alessandro, 2008 2 Andreas Gassner

6 RC servo motor debugging
So lets start with the rc servo motor debugging. The control board which was provided was the Pololu Mini Maestro 24. RC servo motor debugging Motivation Oncilla project Tasks of the project RC servo motor debugging Layout Implemented CPG Tests Analysis Conclusion Experimental setup Walkway / Kistler Diff. configurations Variants/Steel plates Final design Pololu Mini Maestro 24 11/11/2018 Andreas Gassner

7 This picture shows the layout which I used during my semester project with the frequency or tim limitations. Firstly a computer was used to calculate the cpg position which then was transfered throug the USB cable to the Mini Maestro 24. This control boards generates the PWM for all the rc servo motors which are placed on the robot. To do a more stable system and also to get the limitations of the system and to analyze the correct implementation, i tried to get the motors position back to the computer. Unfortunately the Mini Maestro does not provide this solution. So we had to find another solution which i will talk later. Layout Motivation Oncilla project Tasks of the project RC servo motor debugging Layout Implemented CPG Tests Analysis Conclusion Experimental setup Walkway / Kistler Diff. configurations Variants/Steel plates Final design No RC servo motor position feedback possible Analysis of the correct implementation Analysis of the amplitude / frequency 11/11/2018 1 Image taken from: ttp:// 2 Image taken from: Andreas Gassner

8 RC servo motor position feedback
This picture shows the layout which I used during my semester project with the frequency or tim limitations. Firstly a computer was used to calculate the cpg position which then was transfered throug the USB cable to the Mini Maestro 24. This control boards generates the PWM for all the rc servo motors which are placed on the robot. To do a more stable system and also to get the limitations of the system and to analyze the correct implementation, i tried to get the motors position back to the computer. Unfortunately the Mini Maestro does not provide this solution. So we had to find another solution which i will talk later. Layout Motivation Oncilla project Tasks of the project RC servo motor debugging Layout Implemented CPG Tests Analysis Conclusion Experimental setup Walkway / Kistler Diff. configurations Variants/Steel plates Final design RC servo motor position feedback No RC servo motor position feedback possible Analysis of the correct implementation Analysis of the amplitude / frequency 11/11/2018 1 Image taken from: ttp:// 2 Image taken from: Andreas Gassner

9 RC servo motor Debugging
For the analysis i used this CPG with frequencies going from 1.5 Hz to 2.0 Hz. Plus-minus pi over four was chosen as an amplitude. RC servo motor Debugging Motivation Oncilla project Tasks of the project RC servo motor debugging Layout Implemented CPG Tests Analysis Conclusion Experimental setup Walkway / Kistler Diff. configurations Variants/Steel plates Final design Program sends CPG calculated position to control board Test with load (500g), without load Frequency1.5 Hz up to 2.0 Hz (step 0.25 Hz) ai: 5 & ωij: 4 Number of oscillators: 8 (1 tracked) Amplitude: ±π/4 Phase shift: 0 Implemented CPG 1: 𝜃 𝑖 =𝟐 𝝅 𝝂 𝒊 + 𝒋 𝝎 𝒊𝒋 𝒔𝒊𝒏( 𝜽 𝒋 − 𝜽 𝒊 − 𝝓 𝒊𝒋 ) 𝒓 𝒊 = 𝒂 𝒊 ( 𝒂 𝒊 𝟒 𝑹 𝒊 − 𝒓 𝒊 )− 𝒓 𝒊 𝒙 𝒊 = 𝒓 𝒊 (𝟏+𝒔𝒊𝒏( 𝜽 𝒊 ) 11/11/2018 1 From swimming to walking with a salamander robot driven by a spinal cord model, IJSPEERT, Auke Jan et al. , Science, 2007 Andreas Gassner

10 So a CPG calculated position with an amplitude of pi over four and different frequencies was sent to the servo motor. Because no feedback from the servo is possible, we had to do a video aided point tracking. While running the motors are filmed and a point is then tracked frame per frame using the Mtracking tool provided by Kostas. The points then can be analyzed with matlab. The video analyzed points are supposed to be the real points. The whole experience was once made without load and once with a one sided load of 500g. Video point-tracking Motivation Oncilla project Tasks of the project RC servo motor debugging Layout Implemented CPG Tests Analysis Conclusion Experimental setup Walkway / Kistler Diff. configurations Variants/Steel plates Final design 1 11/11/2018 1 Mtracking tool provided by Konstantinos Karakasiliotis Andreas Gassner

11 Analysis of the Results
To analyze the range i ploted the points in matlab compared to the sent values. I then set the range of the sent values to 100% and calculated the corresponding percentage of the video tracked range. As one can see until 1.5 Hz the RC servo motors can follow the imposed positions with and without load. Then we can see a difference. The maximal possible frequency for the RC servo motors would be 2.08 Hz but in this case we dont take into account the accelerations. Analysis of the Results Motivation Oncilla project Tasks of the project RC servo motor debugging Layout Implemented CPG Tests Analysis Conclusion Experimental setup Walkway / Kistler Diff. configurations Variants/Steel plates Final design 100% Percentage of the full range (π/2) Max RC servo motor frequency: 2.08 Hz 11/11/2018 Andreas Gassner

12 Analysis of the Results
To analyze the range i ploted the points in matlab compared to the sent values. I then set the range of the sent values to 100% and calculated the corresponding percentage of the video tracked range. As one can see until 1.5 Hz the RC servo motors can follow the imposed positions with and without load. Then we can see a difference. The maximal possible frequency for the RC servo motors would be 2.08 Hz but in this case we dont take into account the accelerations. Analysis of the Results Motivation Oncilla project Tasks of the project RC servo motor debugging Layout Implemented CPG Tests Analysis Conclusion Experimental setup Walkway / Kistler Diff. configurations Variants/Steel plates Final design 100% Percentage of the full range (π/2) Max RC servo motor frequency: 2.08 Hz 11/11/2018 Andreas Gassner

13 So summarize this part:
The motor position feedback is not possible. So for analyzing the position i made a video analysis. For the correct implementation I had to adjust the interruption time. A real time implementation is necessary. Until now they are made with the system times but other solutions exist. We also saw, that the amplitude of the movement increases when imposing too high frequencies and when putting loads. Conclusion Motivation Oncilla project Tasks of the project RC servo motor debugging Layout Implemented CPG Tests Analysis Conclusion Experimental setup Walkway / Kistler Diff. configurations Variants/Steel plates Final design RC servo motor position feedback Not possible Interruption time Real-time implementation necessary System-timer usage Real time operating system Implement CPG on microcontroller Use better ODE solver method (e.g. Runge-Kutta method) Decreasing amplitude at the motor at high frequencies and with load 11/11/2018 Andreas Gassner

14 Now we will go to my second task which was the design of a walkway for robot locomotion analysis.
Motivation Oncilla project Tasks of the project RC servo motor debugging Layout Implemented CPG Tests Analysis Conclusion Experimental setup Walkway / Kistler Diff. configurations Variants/Steel plates Final design 11/11/2018 Andreas Gassner

15 Walkway So the walkway will be used for verifying gait characteristics for example ground reaction forces already simulated on the computer. So with this walkway we will be able to do the transition from computer simulation to real robots. There will also be a base to install a motion tracking system. Verifying gait characteristics Ground reaction forces Computer simulation to real robots Possibly: installation of a motion tracking system Motivation Oncilla project Tasks of the project RC servo motor debugging Layout Implemented CPG Tests Analysis Conclusion Experimental setup Walkway / Kistler Diff. configurations Variants/Steel plates Final design 11/11/2018 1 Exploiting Compliance with a Cat-sized Quadruped Robot for Trot Gait, TULEU, Alexandre et al. Andreas Gassner

16 Two Kistler force plates
To do so, we the lab possesses two kistler force plates which you can see here. Two Kistler force plates Motivation Oncilla project Tasks of the project RC servo motor debugging Layout Implemented CPG Tests Analysis Conclusion Experimental setup Walkway / Kistler Diff. configurations Variants/Steel plates Final design 11/11/2018 Portable multicomponent force plate for gait- and balance analysis in biomechanics Andreas Gassner

17 Different configurations
While this walkway is used for all kind of robots the quadruped the biped robots and also the amphibots we have to make possible different configurations. But also to analyze different gaits. Some examples are shown here. Different configurations Motivation Oncilla project Tasks of the project RC servo motor debugging Layout Implemented CPG Tests Analysis Conclusion Experimental setup Walkway / Kistler Diff. configurations Variants/Steel plates Final design For AmphiBot, quadruped & biped robots Different gaits 11/11/2018 Andreas Gassner

18 Force plate setup variants
We elaborated two variants, the variant alu and the variant steel. In the variant alu alimine frames are glued with epoxy or screwed to the lab floor. The variant steel uses steel plates to fix the force plates. Because of this three main advantages we choosed the variant steel. Force plate setup variants Variant alu Variant steel Motivation Oncilla project Tasks of the project RC servo motor debugging Layout Implemented CPG Tests Analysis Conclusion Experimental setup Walkway / Kistler Diff. configurations Variants/Steel plates Final design Advantages Low installation costs Frames already present in the lab Disadvantages Height not adaptable Destruction of the lab floor Cost estimation SFr Advantages Adjustable height and declination Avoid vibrations No destruction of the lab floor Flexibility Disadvantages Construction necessary Expensive Inner stress possible Cost estimation SFr 11/11/2018 Andreas Gassner

19 The base for the force plates have to be at least 10 times as heavy as the force plates weicht so around 60kg. The steelplates are made that the different configurations you can see here are possible. Machine foots should avoid lab floor vibrations. The steel plates are providing high inertia. In this configuration while two force plates are on one side two steel plates have to be put together to respect the instructions given in the manual. Steel plates Motivation Oncilla project Tasks of the project RC servo motor debugging Layout Implemented CPG Tests Analysis Conclusion Experimental setup Walkway / Kistler Diff. configurations Variants/Steel plates Final design High inertia Manual: base weight > 10x force plate weight 11/11/2018 Andreas Gassner

20 The base for the force plates have to be at least 10 times as heavy as the force plates weicht so around 60kg. The steelplates are made that the different configurations you can see here are possible. Machine foots should avoid lab floor vibrations. The steel plates are providing high inertia. In this configuration while two force plates are on one side two steel plates have to be put together to respect the instructions given in the manual. Steel plates Motivation Oncilla project Tasks of the project RC servo motor debugging Layout Implemented CPG Tests Analysis Conclusion Experimental setup Walkway / Kistler Diff. configurations Variants/Steel plates Final design High inertia Manual: base weight > 10x force plate weight 11/11/2018 Andreas Gassner

21 Here you can see the final design
Here you can see the final design. Wooden plates will build the walkway, a wooden frame will give the neded height. The middle wooden plates can be changed depending on the chose configuration . Final design Motivation Oncilla project Tasks of the project RC servo motor debugging Layout Implemented CPG Tests Analysis Conclusion Experimental setup Walkway / Kistler Diff. configurations Variants/Steel plates Final design 11/11/2018 Andreas Gassner

22 So for summarize: A walkway was designed and two variants for foce plate fixation were proposed. The variant steel was recommended and construction files are provided. An order for all the material was prepared. A request for price and feasibility of the steel plates has been made. conclusion Motivation Oncilla project Tasks of the project RC servo motor debugging Layout Implemented CPG Tests Analysis Conclusion Experimental setup Walkway / Kistler Diff. configurations Variants/Steel plates Final design Walkway with embedded force plates Two variants proposed Variant steel recommended Construction files provided Order prepared Request for price and feasibility 11/11/2018 Andreas Gassner

23 Thank you for your attention
Thank you for your attention. I’m sure you have some questions. Questions? Thanks to: Professor Auke Jan Ijspeert Supervisors Alexander Spröwitz & Rico Möckel Jonathan Grizou, Rolando Rodas, Laurenz Notter

24 11/11/2018 Andreas Gassner

25 So for finishing the small oncilla platform i have to resolve the timer problem i mentioned, then i can implement the CPG programmed in C# and the small oncilla should be ready for some first tests. Concerning the large oncilla, firstly i have to make some reading on the RoBoard RB-110, which is the controller board of the large Oncilla. Then the brushless dc motors have to be implemented. For executing the tests on both Oncillas the experimental setup has to be created. Future work Order and build the walkway Build the robot and implement the program Tests on the platform using the experimental setup Possibly installation of a motion tracking system Implementation of a more complex gait able to produce a locomotion movement Implementation of a real time solution 11/11/2018 Andreas Gassner

26 Effect of parameters ωij = 0 , ai = 100 ωij = 1 , ai = 100
11/11/2018 Andreas Gassner

27 Debugging Cropped sine waves (timer problem)
Maestro control center (min-max values) Video point-tracking analysis 11/11/2018 Andreas Gassner


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