Design and Implementation of the Bio-inspired Facial Expressions for Medical Mannequin

Abstract

A medical mannequin is an intelligent device used in hospitals for providing medical students hands-on learning experience without the risk of injury to a human subject. The closer these mannequins become to mimicking the functionality of a human being, the better the quality of training. In this paper, we report the development of a biomimetic mechatronic face with eyes, skin and neck having human-like performance. The face was created with 13 degrees of freedom to incorporate all the action units necessary to reconstruct 7 basic expressions. The eyes were able to perform blinking, movement, iris dilation, and object tracking. The neck was a Stewart Platform with 6 degrees of freedom and was capable of translation and rotation that mimic the human vertebrae. A durable artificial skin was developed using silicone elastomer to replicate the texture and appearance of real human skin.

Appendices

Appendix

Coordinates for neck attachment points for bottom (B) and top (T) plates.

	X	Y	Z
B1	$\frac{\sqrt{3}}{6}(2b+d)$	$\frac{d}{2}$	0
B2	$-\frac{\sqrt{3}}{6}(b-d)$	$\frac{(b+d)}{2}$	0
B3	$-\frac{\sqrt{3}}{6}(b+2d)$	$\frac{b}{2}$	0
B4	$-\frac{\sqrt{3}}{6}(b+2d)$	$-\frac{b}{2}$	0
B5	$-\frac{\sqrt{3}}{6}(b-d)$	$-\frac{(b+d)}{2}$	0
B6	$\frac{\sqrt{3}}{6}(2b+d)$	$-\frac{d}{2}$	0
T1	$\frac{\sqrt{3}}{6}(a+2c)$	$\frac{a}{2}$	0
T2	$\frac{\sqrt{3}}{6}(a-c)$	$\frac{(a+c)}{2}$	0
T3	$-\frac{\sqrt{3}}{6}(2a+c)$	$\frac{c}{2}$	0
T4	$-\frac{\sqrt{3}}{6}(2a+c)$	$-\frac{c}{2}$	0
T5	$\frac{\sqrt{3}}{6}(a-c)$	$\frac{(a+c)}{2}$	0
T6	$\frac{\sqrt{3}}{6}a+2c$	$-\frac{a}{2}$	0

Equations for coordinates of top plate with respect to bottom plate of Stewart platform

$$\begin{aligned} X_{T1}&=x_T -(a*(cb*sz-cz*sa*sb))/2\\&\quad +(3^{(1/2)}*(cb*cz+sa*sb*sz)*(a+2*c))/6 \\ Y_{T1}&=y_T +(a*ca*cz)/2\\&\quad +(3^{(1/2)}*ca*sz*(a+2*c))/6 \\ X_{T1}&=z_T +(a*(sb*sz+cb*cz*sa))/2\\&\quad -(3^{(1/2)}*(cz*sb-cb*sa*sz)*(a+2*c))/6 \\ X_{T2}&=x_T -(cb*sz-cz*sa*sb)*(a/2+c/2)\\&\quad +(3^{(1/2)}*(cb*cz+sa*sb*sz)*(a-c))/6 \\ Y_{T2}&=y_T +ca*cz*(a/2+c/2)\\&\quad +(3^{(1/2)}*ca*sz*(a-c))/6 \\ Z_{T2}&=z_T +(sb*sz+cb*cz*sa)*(a/2+c/2)\\&\quad -(3^{(1/2)}*(cz*sb-cb*sa*sz)*(a-c))/6 \\ X_{T3}&=x_T -(c*(cb*sz-cz*sa*sb))/2\\&\quad -(3^{(1/2)}*(cb*cz+sa*sb*sz)*(2*a+c))/6 \\ Y_{T3}&=y_T +(c*ca*cz)/2\\&\quad -(3^{(1/2)}*ca*sz*(2*a+c))/6 \\ Z_{T3}&=z_T +(c*(sb*sz+cb*cz*sa))/2\\&\quad +(3^{(1/2)}*(cz*sb-cb*sa*sz)*(2*a+c))/6 \\ X_{T4}&=x_T +(c*(cb*sz-cz*sa*sb))/2\\&\quad -(3^{(1/2)}*(cb*cz+sa*sb*sz)*(2*a+c))/6 \\ Y_{T4}&=y_T -(c*ca*cz)/2\\&\quad -(3^{(1/2)}*ca*sz*(2*a+c))/6 \\ Z_{T4}&=z_T -(c*(sb*sz+cb*cz*sa))/2\\&\quad +(3^{(1/2)}*(cz*sb-cb*sa*sz)*(2*a+c))/6 \\ X_{T5}&=x_T +(cb*sz-cz*sa*sb)*(a/2+c/2)\\&\quad +(3^{(1/2)}*(cb*cz+sa*sb*sz)*(a-c))/6 \\ Y_{T5}&=y_T -ca*cz*(a/2+c/2)\\&\quad +(3^{(1/2)}*ca*sz*(a-c))/6 \\ Z_{T5}&=z_T -(sb*sz+cb*cz*sa)*(a/2+c/2)\\&\quad -(3^{(1/2)}*(cz*sb-cb*sa*sz)*(a-c))/6 \\ X_{T6}&=x_T +(a*(cb*sz-cz*sa*sb))/2\\&\quad +(3^{(1/2)}*(cb*cz+sa*sb*sz)*(a+2*c))/6 \\ Y_{T6}&=y_T -(a*ca*cz)/2\\&\quad +(3^{(1/2)}*ca*sz*(a+2*c))/6 \\ Z_{T6}&=z_T -(a*(sb*sz+cb*cz*sa))/2\\&\quad -(3^{(1/2)}*(cz*sb-cb*sa*sz)*(a+2*c))/6 \\ \end{aligned}$$

34 Predefined Expressions

Happy	Angry	Disgusted	Surprised	Suspicious	Sarcastic	Sad
Happy	Angry	Disgusted	Surprised	Suspicious	Sarcastic	Sad
Ecstatic	Upset	Bothered	Astonished	Curious	Crazy	Depressed
Content	Aggravated	Jealous	Fearful	Arrogant	Disrespectful	Mournful
Joyful	Furious	Offended	Confused	Untrusting		Embarrassed
Hopeful	Spiteful		Bewildered	Interested		Shy
				Disturbed		Guilty