torque.clj

(ns torque-sim.core)

;;I want to calculate the strenght of motors needed for a robot of various parameters

(defn get-motor-strength
  [robot-femur-length robot-torso-weight]
  ()
  )

(def g 9.8)

(defn torque
  ([a m l] (* a m l))
  ([f l] (* f l)))

(defn gravitational-torque
  [mass length]
  (torque g mass length))

(defn moment-of-inertia
  [t m values]
  (case t
    :point (let [distance-of-point-from-axis (first values)]
             (* m (java.lang.Math/pow
                   distance-of-point-from-axis 2)))))

(defn acceleration-from-d-and-t
  [d t]
  (/ (* 2 d) (java.lang.Math/pow t 2)))

(defn max-rpm [a t]
  (* 60 (/ (* a t) (* 2 3.14))))

(defn nm->kg-cm [nm]
  (* 100 (/ nm 9.8)))

(defn torque-required
  ([mass               ;;kg
    radial-acceleration ;;rads/sec^2
    length              ;;meters
    ]

   (*
    (/ 1 9.8)
    (* 100)
    (+ (gravitational-torque mass length)
       (torque (moment-of-inertia :point mass [length])
               radial-acceleration)))
   ;;rv returned in kg-cm
   )
  ([mass
    time
    radians
    length-of-arm
    & {:keys [motor-max-rpm]
       :or {motor-max-rpm 600}}
    ]

   (let [a
         (acceleration-from-d-and-t (/ radians 2)
                                    (/ time 2))
         max-rpm
         (max-rpm a time)

         torque-required 
         (torque-required mass a length-of-arm)

         gearing-ratio (/ motor-max-rpm max-rpm)]

    {:torque-required torque-required

     :max-rpm max-rpm 

     :gearing-ratio  gearing-ratio

     :motor-torque-required (/ torque-required gearing-ratio)})))

usage.clj

 ;;22 kg robot to take 1 second to stand (90 degree feumur movement) with a femur length of .2m . Also, stepper motors effecient rpm maxes at around 500.
 
 (torque-required 22 1 (/ 3.14 2) 0.2 :motor-max-rpm 500)