1. CURSO-20061.1 Topics about of design and construction of experimental parallel robots in DISAM (based on examples) Roque Saltaren Universidad Politécnica de Madrid, SPAIN rsaltaren@etsii.upm.es

2. Universidad Politécnica de Madrid 1.2 Contents 1.Relevant characteristics of some parallel robots develops for biomechanics applications 2.Kinematics modeling and design considerations 3.Dynamics modeling and design considerations 4.Mechanical design and construction 5.Hardware and control  Hardware architecture based on PC- 104/PowerPC + LAN  Hardware architecture based on multiaxis card  Hardware architecture based on dSPACE 6.User interfaces 7.Real time operative systems (RTOS). 8.Integration 9.Conclusions: Real prototypes or scale prototypes: The best techniques.

3. Universidad Politécnica de Madrid 1.3 …Relevant characteristics Spherical pivot parallel platforms for robots (3RPS, 3PRS and 3RRS)  Applications: Prosthesis, endoscopies, humanoid necks, shoulders and eyes  Three types of kinematics configurations: End effectors articulate by spherical joints  Short radius of turn  Reduce work space  Robustness  Easy of assembly and machining

4. Universidad Politécnica de Madrid 1.4 …Relevant characteristics …..Spherical pivot platforms for robots Mechanical parts can impose limitations: Standard spherical joints works with: +/- 30º Special spherical joints can allows +/- 90º Actuators (better options) Powering by cable  High technology cables: FORTATECH (very good option!) Powering by ball screws and servomotors  SKF (low cost) + Maxonmotor;  SteinMeyer (high cost) + Maxonmotor (micro ball screws : 3 mm. aprox 350 eur.) Powering by servomotors (aprox.

5. Universidad Politécnica de Madrid 1.5 …Relevant characteristics …..The 3 RRR configuration  The Agile Eye topics  Easy of machining  Servomotor + gear reductor + arm = high torque  Very fast

6. Universidad Politécnica de Madrid 1.6 ….Relevant characteristics …3UPU platforms  Based on linear actuators  With special universal joints = high work space  Singular configurations  Very simple, except by the rings, that need take account de P point (the P point is allow machining the rings with inclined planes to aligning the axis of the universal joints  Estimated costs, for example: Maxonmotor 20 W + Gear Reductor Maxon + SKF ball screw + machining = 1000 eur. Rings: less of 150 euros Amplifiers Maxon : 170 eur.

7. Universidad Politécnica de Madrid 1.7 ….Relevant characteristics 2UPS-1RU Chen platform The more robust  Eccentric rotation point!  Two UPU limbs  One RU limb (required a special universal joint)  Extreme orientations  What is a special universal joint?

8. Universidad Politécnica de Madrid 1.8 …Relevant characteristics Example-1. Performance evaluation of spherical parallel platforms for humanoid robots

9. Universidad Politécnica de Madrid 1.9 …Relevant characteristics Example-1. …Performance evaluation Goals: Allows the work space of the neck or shoulder !

10. Universidad Politécnica de Madrid 1.10 …Relevant characteristics Example-1. …Performance evaluation

11. Universidad Politécnica de Madrid 1.11 …Relevant characteristics Example-1. …Performance evaluation

12. Universidad Politécnica de Madrid 1.12 …Relevant characteristics Example-1. …Performance evaluation

13. Universidad Politécnica de Madrid 1.13 …Relevant characteristics Example-1. …What is the better option ?

14. Universidad Politécnica de Madrid 1.14 …Relevant characteristics …..Stewart-Gough parallel robots Mechanical parts can impose limitations: Standard spherical joints works with: +/- 30º Special spherical joints can allows +/- 90º Actuators (better options!) Powering by ball screws and servomotors  SKF + Control Techniques Low cost: Ball screws (medium precision) High cost: Ruler screws: very good precision (aprox. 350 eur.)  Control Techniques servomotors Examp. UNIMOTOR + Amplifier (800- 2000 eur. An experimental medium size S-G platform can to have a cost of: 10.500 eur. An experimental small size S-G platfor can to have a cost of: 6.000 eur.

15. Universidad Politécnica de Madrid 1.15 …Relevant characteristics …..Stewart-Gough parallel robots  How allows the maximum work space ? Changing the spherical and universal joints by special joints!!

16. Universidad Politécnica de Madrid 1.16 …Relevant characteristics ….How allows the maximum work space ?

17. Universidad Politécnica de Madrid 1.17..Kinematics modeling and design consideration Two problematic aspects:  Singularities (restrictions over the work space!!) Don’t forget the theory! (Hunt, Fletcher, Di- Gregory, etc.) Modeling with screw based jacobian Path planning control in base to the Conditioning Index CI, and Global Conditioning Index GCI  Direct kinematics solution: Numerical methods based on multibody mechanics and Newton- Raphson methods!!  Design considerations: GCI index very useful to know and understand the machine

18. Universidad Politécnica de Madrid 1.18 …Dynamics modeling and design considerations For a Stewart-Gough platform:  Dynamics modeling: Multibody dynamics: we are use two ways: 1.Programming with ADAMS (after of know how program with ADAMS, very fast develops!) the problem is that the ADAMS language is not easy!! 2.Programming with Matlab: Is better, but is necessary to have a very good acknowledges on multibody dynamics!! and to have some experts in the group! 3.For real time RT, we works in multibody dynamics for RT: we used OOD, C++ + UML + RTLinux.

19. Universidad Politécnica de Madrid 1.19 Mechanical design and construction The first prototype: Is necessary to have a PERFECT first experimental prototype??.  Usually not!! In many occasion we need first demonstrate some hypothesis! In many occasion we need allows that the control and software run!  Really we need a prototype in real scale?? Not, we are sure that in many occasions to demonstrate the hypothesis and develop computational algorithms is sufficiently to work with scaleable prototypes!!.

20. Universidad Politécnica de Madrid 1.20 …Mechanical design and construction A case.  We are developing an underwater parallel robot We should optimized the useful internal space to assembly the control and power hardware, because this:  The geometrical form of the robot hull is very complicated  The length of the hull is diffuse because we will need aggregate more hardware in the future  The machining costs can be high if we used an adjusted geometry to the hardware dimensions

21. Universidad Politécnica de Madrid 1.21 …Mechanical design and construction The solution adopted.  We decide use an engineering plastic with non-hygroscopic performance, soldering and adhesive good properties (many plastics can not solder!!)  The plastic selected is appropriate to machining (for example, we can use joints with mechanical screws)  We use Delrin Acetal plastic (Du Pont)  The plastic weight 1/8 part of the steel!!  The design limit the machining to 2 ½ D  The design is modular  We can use adhesives  Machining with water jet cutting  Assembly with mechanical screws + GORE Tex seals and adhesives

22. Universidad Politécnica de Madrid 1.22 Hardware and control In many applications is sufficiently with the next hardware architecture:  Based on PC-104 + RS 485 LAN + Ethernet  Multiaxis control base on multipoint RS-485 Duplex Network to 115200 Bps.  Capacity to control many axis (256)  Develop below QNX real time system or RT Linux  Flash SD memory (2 G)  And the better!!: less of 1000 eur We used this card to control a S-G parallel robot with 12 Step servomotors. We used Stepper motors to avoid used encoder and its electric cables The servomotors power and control hardware are prepared to connect in Network (Duplex RS-485) !!! PC compatible Single Board Computer with 133 MHz AMD 586 processor. 32-64 MB SDRAM 10/100 Ethernet PCMCIA socket Compact Flash socket Optional A/D & DAC 2 COM ports 23 DIO PC/104 expansion bus 2 MB Flash drive Technologic Systems, Incorporated 16610 East Laser Drive, Suite 10 Fountain Hills, AZ 85268 480-837-5200 FAX 837-5300 info@embeddedx86.com http://www.embeddedx86.com/