View source for TURTLE 8-Wheeled Base

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| style="background:LightBlue; color:black; font-size:135%" align="center" | '''Robot Links'''
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| style="background:LightGrey; color:black; font-size:115%" align="left" | '''Author'''
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| style="background:white; color:black;" align="left" | [http://www.tue.nl/en TU/e]
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| style="background:white; color:black;" align="left" | [http://www.tue.nl/en/university/departments/mechanical-engineering/research/research-groups/control-systems-technology/ CST Group, TU/e]
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| style="background:LightGrey; color:black; font-size:115%" align="left" | '''CAD Files'''
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| style="background:white; color:black;" align="left" | [https://gitlab.tue.nl/tech-united-eindhoven/rop/-/tree/master/TURTLE/Mechanical%20Designs/3D%20CAD%20Models/STEP/TURTLE-8w-Assembly.STEP STEP]
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| style="background:LightGrey; color:black; font-size:115%" align="left" | '''Electronic Drawings'''
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| style="background:white; color:black;" align="left" | [https://gitlab.tue.nl/tech-united-eindhoven/rop/-/tree/master/TURTLE/Electrical%20Designs/Wiring%20Schemes/E-schema_8w.pdf PDF]
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| style="background:LightGrey; color:black; font-size:115%" align="left" | '''Software'''
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| style="background:white; color:black;" align="left" | [https://gitlab.tue.nl/tech-united-eindhoven/Turtle3 Software]
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|style="background:white; color:black;" align="left" | [https://robocup.wtb.tue.nl/svn/techunited/trunk/src/Turtle2/Motion/low_level_control_lib.slx low_level_control_lib.slx]
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| style="background:LightGrey; color:black; font-size:115%" align="left" | '''Software Flow Charts'''
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| style="background:white; color:black;" align="left" | [http://www.techunited.nl/media/images/Tech%20United%20-%20Software%20Scheme.pdf|Software Scheme]
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| style="background:white; color:black;" align="left" | [http://www.techunited.nl/simulink/motion_turtle_slwebview_files/index.html Motion]
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| style="background:white; color:black;" align="left" | [http://www.techunited.nl/simulink/vision_turtle_slwebview_files/index.html Vision]
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| style="background:white; color:black;" align="left" | [http://www.techunited.nl/simulink/worldmodel_slwebview_files/index.html World Model]
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| style="background:LightGrey; color:black; font-size:115%" align="left" | '''License'''
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| style="background:white; color:black;" align="left" | [https://robotics.wtb.tue.nl/svn/rop/TURTLE/License/ License Files]
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[[TURTLE|TURTLE]]: [[TURTLE Base|Base]] | [[TURTLE Upper Body|Upper Body]] | [[TURTLE Ball Handling and Kicking Mechanism|Ball Handling and Kicking Mechanism]] | [[TURTLE Goalkeeper|Goalkeeper]] | [[TURTLE 8-Wheeled Base|8-Wheeled Base]]



__TOC__

= Robot Summary = 
As an alternative for the three-wheeled [[TURTLE Base|base]] of the [https://msl.robocup.org/ RoboCup Middle Size League] soccer robots of Tech United Eindhoven, an eight-wheeled version was designed consisting of four wheel sets, each having two hub-drive wheels. Figure 1 depicts such a wheel set, whereas the realization of the system is shown in Figure 2. The main advantages compared to the three-wheeled platform are the possibility to apply the torque delivered by the motors in the desired direction in order to achieve a higher acceleration in this direction. 

* Author: [http://www.tue.nl/en/university/departments/mechanical-engineering/research/research-groups/control-systems-technology/CST Group, TU/e]
* License: [http://www.ohwr.org/projects/cernohl/wiki CERN OHL v.1.1]
* Software: [https://gitlab.tue.nl/tech-united-eindhoven/Turtle3 https://gitlab.tue.nl/tech-united-eindhoven/Turtle3]
* Simulink Control Implementation: [https://gitlab.tue.nl/tech-united-eindhoven/Turtle3/Motion/low_level_control_lib.slx low_level_control_lib.slx]. Chose the "Turtle8W" subsystem to find the implementation of the control architecture of the 8-wheeled base.

Contributions in publications about this platform  can be found in 

Houtman W. et al. (2019) [https://link.springer.com/chapter/10.1007/978-3-030-35699-6_42 Tech United Eindhoven Middle-Size League Winner 2019]. In: Chalup S., Niemueller T., Suthakorn J., Williams MA. (eds) RoboCup 2019: Robot World Cup XXIII. RoboCup 2019. Lecture Notes in Computer Science, vol 11531. Springer, Cham

Douven Y. et al. (2019) [https://link.springer.com/chapter/10.1007%2F978-3-030-27544-0_34 Tech United Eindhoven Middle Size League Winner 2018]. In: Holz D., Genter K., Saad M., von Stryk O. (eds) RoboCup 2018: Robot World Cup XXII. RoboCup 2018. Lecture Notes in Computer Science, vol 11374. Springer, Cham

<gallery class="center" widths="225" heights="300" >
Image:8w-wielSet.png|Figure 1: Wheel Set, including the passive lateral degree of freedom indicated with the white (dotted) lines and the rotational degree of freedom which can be manipulated by a force difference applied to the ground by both wheels.
Image:8W metKapenBalUitgeknipt.png|Figure 2: Realization of the system
</gallery>

= 3D Viewer =
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= Overview = 
The eight-wheels system is a redesign of the three wheeled version of the Tech United RoboCup Team Limited Edition (TURTLE) robots. As such, the base has been reconsidered, while the [[TURTLE Upper Body|the upper body]] and the [[TURTLE Ball Handling and Kicking Mechanism|the ball handling and kicking mechanism]] have been reused. Therefore, the focus of the hardware elaborated on this page is on the wheel sets and the assembly of the entire system.

This platform consists of four wheel sets, each having two hub-drive wheels. As such, the platform is five  times  over-constrained.  To  avoid  an  over-constrained  design,  each  wheel set  has  an  internal  degree  of  freedom. This degree of freedom is visualized in Figure 1 by the white lines.  The  last platform-constraint  is  addressed  by  a hinging  axle  at  the  back  of  the  robot, which is shown in Figure 3. By using slip rings for powering the wheel sets and communicating the control signals, the rotation of the wheels is unconstrained in both directions.


[[File:8w-BaseView.jpg|400px|Image: 400 pixels|thumb|center|Figure 3: Wheel configuration including the base plate and hinging axle of the 8-wheeled soccer robot]]

= Specifications =

== Wheel Sets ==
•	Wheel radius: 0.056 meter<br>
•	Lateral wheel distance: 0.056 meter<br>
•	Motor velocity constant: 135 revolutions per minute per volt <br>
•	Motor torque constant: 135  Newton meter per ampere<br>
•	Motor resistance: 0.072 Ohm<br>

== Communication ==

Custom EtherCat module consisting of 

''Observed signals:'' <br>
•	Measured orientation of the wheel set (19 bit encoder)<br>
•	Measured position of each wheel (16 bit encoder)<br>
•	Measured velocity of each wheel<br>
•	Safe torque off status<br>
•	Warning & error statuses<br>
•	Measured Negative Temperature Coefficient (NTC) resistor for temperature observations<br>

''Actuation Signals:'' <br>
•	Control Mode: position, velocity or current control <br>
•       Corresponding setpoint <br>

= Video =
The video on the left indicated the first match appearance of the Eight-wheeled system at the RoboCup Portuguese Open 2019. The eight-wheeled system, indicated with number 7, can be discriminated from the other robots based on its square base. The video on the right demonstrates the functionalities of the system on the practice field of Tech United Eindhoven.

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{{#ev:youtube|nF_6aQLqb-Y}} {{#ev:youtube|4ZPNy5IjWFQ}}}</div>

= License =
Copyright Eindhoven University of Technology 2020. <br>
<br>
This documentation describes Open Hardware and is licensed under the CERN OHL v. 1.1. <br>
You may redistribute and modify this documentation under the terms of the CERN OHL v.1.1. (http://ohwr.org/cernohl). <br>
This documentation is distributed WITHOUT ANY EXPRESS OR IMPLIED WARRANTY, INCLUDING OF MERCHANTABILITY, SATISFACTORY QUALITY AND FITNESS FOR A PARTICULAR PURPOSE. Please see the CERN OHL v.1.1 for applicable conditions.