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