Measurement Systems and Applications Mariolino De Cecco Antonio Selmo Michele Confalonieri

1. Measurement Systems and Applications Mariolino De Cecco Antonio Selmo Michele Confalonieri

2. Force Panel The instrument employed

3. How its electronics work? [Antonio Selmo] Design and purpose of the FP [a couple of frontal lessons] Measurements for Diagnostics [study and identification of the HTF] Rehabilitation and its quantification (measure of indexes of performance) [development of serious games with processing] Principles of human diagnosis and rehabilitation [doct Guandalini and Tomasi] Achronims: Fprce Panel – FP Human Transfer Function - HTF Logic of the Course

4. Application: identification of human transfer function for dexterity assessment and serious games for rehabilitation • Course: • frontal lessons (few) • exercitation with matlab • building of the application with Processing • visit to a clinic • Method: • study of touch technology • study of signal analog elaboration and conversion • acquisition of human data • signal processing • Exam: • oral discussion • homework Material of the course can be found at http://www.miro.ing.unitn.it Organization and final examination

5. VERITAS Project Project number: 247765 Project acronym: VERITAS Project full title: Virtual and Augmented Environments and Realistic User Interactions To achieve Embedded Accessibility DesignS Site: http://www.veritas-project.eu/ Starting date: 1 January 2010 Duration: 48 MonthsVERITAS is an Integrated Project (IP) within the 7th Framework Programme, Theme FP7-ICT-2009.7.2, Accessible and Assistive ICT

6. Design and purpose of the FP - VERITAS Project Virtual and Augmented Environments and Realistic User Interactions To achieve Embedded Accessibility DesignS Method SP1: development of virtual users SP2: development of the simulation platform SP3: validation OBJECTIVE develop virtual humans for accessibility design in virtual simulation of ICT and non ICT products • UNITN activities • Modeling • Measurement

7. Systems developed: Garment based Motion Capture: Ga-MoCap Multi-axis load cell Force Panel VERITAS Project - measurement systems developed

8. Diagnostics by human dexterity estimation Requirements: Measure position of the touch Measure the applied force Store the above for path and trajectories Accuracy and sampling frequency able to reveal human dexterity Visual feedback Idea: “Force Panel” Display LCD Touch panel Force transducers Design and purpose of the FP - requirements

9. Stato dell’arte Touch screen LCD and cameras Graph tablets Design and purpose of the FP - state of the art

10. Stato dell’arte joystick Aptics devices and virtual reality Design and purpose of the FP - state of the art

11. Force Panel Design and purpose of the FP - Design

12. Schema della struttura(disposizione dei vincoli) Horizontal use Vertical use 3 load cells = perpendicular to LCD = parallel to LCD Design and purpose of the FP - Design

13. Tipologie di vincolo considerate Spherical joints wires wires 2 solutions ! Design and purpose of the FP - Design

14. Design and purpose of the FP - Design

15. Variante con teste a snodo mechanical design: spherical joint

16. mechanical design: wires

17. mechanical design: wires constraints

18. mechanical design: wires constraints

19. Requirements: No buckling No finger force through the blues Diameter 1 mm Wires with load cell Length 10 mm (due to physical constraints) wires Length 30 mm (FEM analysis → finger force < 0.3 %) F mechanical design: wires length

20. Lunghezza dei fili horizontal Vertical Worst case for buckling Worst case for force leakage mechanical design: wires length

21. Critical length ≈ 65 mm Force lost: Moments ≈ 10-3 – 10-6 Nm mechanical design: wires length

22. VGA Force sensors Touch panel PC LCD Force Conditioning 2 x DIGITAL OUT USB µController 2 x ANALOG IN 3 x ANALOG IN System design: overall layout

23. A touch screen is a 2-dimensional sensing device constructed of 2 sheets of material separated slightly by spacers A common construction is a sheet of glass providing a stable bottom layer and a sheet of Polyethylene (PET) as a flexible top layer The 2 sheets are coated with a resistive substrate, usually a metal compound called Indium Tin Oxide (ITO). The ITO is thinly and uniformly sputtered onto both the glass and the PET layer Tiny spacers are placed between the 2 sheets in order to prevent false touch When the PET film is pressed the two resistive surfaces meet. This position can be read as illustrated in next slides Touch position measurement circuit

24. Indium tin oxide (ITO, or tin-doped indium oxide) is a solid solution of indium(III) oxide (In2O3) and tin(IV) oxide (SnO2), typically 90% In2O3, 10% SnO2 by weight. It is transparent and colorless in thin layers while in bulk form it is yellowish to grey. In the infrared region of the spectrum it is a metal-like mirror. • Indium tin oxide is one of the most widely used transparent conducting oxides because of its two chief properties: • its electrical conductivity • optical transparency Touch position measurement circuit

25. 5 V y+ L VS - sense GND R0 is the total resistance of the substrate RT is the touch resistance Touch position measurement circuit

26. Reading the x coordinate is similar Note that in the equivalent circuit there are capacitive effects that lead to a certain delay that usually is less than 10 ms Touch position measurement circuit

27. Electronics scheme

28. Circuito di condizionamento Pre-Amplificazione e Filtro analogico passa basso Bessel V ordine Output cella Shift del segnale (μC legge solo tensioni positive) μC Amplificazione Cella di carico Alim. cella Alim. condiz. (± 15 V DC) DC / DC Alimentazione (12 V DC) Conditioning unit

29. Conditioning unit

30. Full Wheatstone bridge Bessel lowpass 5° order Gain and offset adjustment: Arduino reads only positive voltages (0 – 5 V) Conditioning unit

31. RISPOSTA TEMPORALE AL GRADINO DEL FILTRO PASSA BASSO DEL 5° ORDINE (Risposta di Bessel con frequenza di taglio 1 kHz) No sovraelongation 50s Tempo di assestamento 500 s 20s Conditioning unit

32. Arduino UNO Inizializzazioni (costanti, variabili e pin μC) Alimentazione lungo X Attesa assestamento circuito RC X PC Lettura valore X Alimentazione lungo Y Attesa assestamento circuito RC Y Lettura valore Y F1 Lettura valore F1 F2 Lettura valore F2 F3 Lettura valore F3 sw design: embedded system

33. t [ms] TASK 1 – Arduino TASK 3 – PC TASK 2 – PC 5 0 15.2 8 10.1 10.2 5.1 Gestione delle immagini in relazione alle risposte di chi sta di fronte al pannello PIN per lettura X t assest. RC 25.2 Read X PIN per lettura Y Read F1, F2, F3 nel t assest. RC Read Y Invio dati via RS-232 Ricezione dati ed applicazione modello di taratura 2 task paralleli su PC: - uno segue l’Arduino, - uno è indipendente sw design: task analysis

34. Acquisition Inizializzazioni Lettura RS-232 Riconoscimento stringa Distinzione segnali Eventuali operazioni di filtraggio Operazioni di taratura Elaboration and graphical output Inizializzazioni Attesa inizio acquisizione Calcolo della tara del sistema Elaborazione (gestione delle immagini in relazione all’interazione con l’utente) sw design: two independent tasks on the PC

35. Touch position (resistive touch) Force (load cell) Touch position (load cell) Calibration

36. Force Panel - calibration

37. Measurement model: Linear behaviour on both directions No interactions uncoupled modelling xa [bit] xm = f (xa) ym = f (ya) xm [pixel] ya [bit] ym [pixel] calibration: position

38. Non-linear behaviour for: Touch position Force FT [bit] Fm[N] = f (Fa , xm , ym) Fm [N] xm [pixel] ym [pixel] calibration: force

39. For N measurements made in different positions and with different forces it is possible to build the following linear relation Than, with a pseudoinverse computation, the 10 coefficients of the polynomial model are estimated WORK IN CLASS Force Panel - calibration: force

40. The pseudoinverse computation gives the 10 coefficients of the polynomial model: NOTE: ATA is generally a square and full rank matrix WORK IN CLASS Force Panel - calibration: force

41. Files given: • read_float.m How to use read_float : jj = 1 ; % numero file file = ['dati_celle_armon_', num2str(jj), '.txt'] ; dati = read_float(file, ',', ':') ; clc Dati = cell2mat(dati); % grammi -> Newton Dati(:,1) = Dati(:,1)*(9.81/1000) ; WORK IN CLASS Force Panel - calibration: force

42. % Data are saved on 9 files “dati_celle_armon_1…9.txt” As follows on columns: % 1 -> calibration load [g] % 2 -> x position [pixel] % 3 -> y position [pixel] % 4 -> load cell 1 (in alto) [N] % 5 -> load cell 2 (in basso a sx) [N] % 6 -> load cell 1 (in basso a dx) [N] % 7 -> load cell sum [N] WORK IN CLASS Force Panel - calibration: force

43. chi2gof Chi-square goodness-of-fit test on the vector e Performs a chi-square goodness-of-fit test for discrete or continuous distributions. The test is performed by grouping the data into bins, calculating the observed and expected counts for those bins, and computing the chi-square test statistic SUM((O-E).^2./E), where O is the observed counts and E is the expected counts. This test statistic has an approximate chi-square distribution when the counts are large. WORK IN CLASS Force Panel - calibration: force

44. Procedure: • With the pseudoinverse computation estimate the 10 coefficients of the proposed polynomial model taking one data file at your choice • Apply the estimated coefficients to the model to predict (validate) the model behaviour using a different data file • Analyse the residuals and the validation behaviour • Apply the chi2gof test to verify the randomness of the residuals • Try to choose different mathematical models and see how the chi2gof test performs WORK IN CLASS Force Panel - calibration: force

45. F1a [bit] xm [pixel] xm = f (F1a ,F2a ,F3a) ym = f (F1a ,F2a ,F3a) F2a [bit] ym [pixel] F3a [bit] 1 3 2 Force Panel – calibration position

46. Nail Finger finger horizontal Yellow: resistive touch Blue: load cell reconstruction Force Panel – calibration position