added physics model description

Modelling/physics model.txt

@@ -0,0 +1,21 @@
+Pt = Ph + Pm = Pp + Pa + k*v + f*v²
+Pp = max(0, -m*g*vv)
+Pa = 1/2*m*(vdt² - v0²)/dt = m*a*(v0 + 1/2*a*dt)
+
+Pt: total power, in W
+Ph: mechanical human power, in W
+Pm: mechanical motor power, in W ; this is not the electrical power, as the motor has an efficiency lower than 1
+Pp: potential power (in W, due to potential energy change)
+Pa: acceleration power (in W, due to kinetic energy change)
+k: kinetic friction coefficient (dry friction)
+f: fluid friction coefficient (air friction)
+v: velocity, in m/s
+vv: vertical velocity (in m/s, positive => going uphill)
+g: gravity constant (-9.8 m.s⁻²)
+m: mass in kg
+
+vehicle constants:
+- mass (m), including driver, passengers and other payloads ; easy to measure directly
+- kinetic friction coefficient (k) ; difficult to measure, needs to be estimated from monitoring data
+- fluid friction coefficient (f) ; difficult to measure, needs to be estimated from monitoring data
+