Class: DrivingPhysics::Car

Inherits:
Object
  • Object
show all
Defined in:
lib/driving_physics/car.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(tire:, powertrain:) {|_self| ... } ⇒ Car

Returns a new instance of Car.

Yields:

  • (_self)

Yield Parameters:



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# File 'lib/driving_physics/car.rb', line 9

def initialize(tire:, powertrain:)
  @num_tires = 4
  @tire = tire
  @env = @tire.env
  @powertrain = powertrain
  @body_mass = 1000.0
  @frontal_area = DrivingPhysics::FRONTAL_AREA
  @cd = DrivingPhysics::DRAG_COF

  yield self if block_given?
end

Instance Attribute Details

#body_mass ⇒ Object

Returns the value of attribute body_mass.



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# File 'lib/driving_physics/car.rb', line 7

def body_mass
  @body_mass
end

#cd ⇒ Object

Returns the value of attribute cd.



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# File 'lib/driving_physics/car.rb', line 7

def cd
  @cd
end

#env ⇒ Object (readonly)

Returns the value of attribute env.



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# File 'lib/driving_physics/car.rb', line 6

def env
  @env
end

#frontal_area ⇒ Object

Returns the value of attribute frontal_area.



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# File 'lib/driving_physics/car.rb', line 7

def frontal_area
  @frontal_area
end

#num_tires ⇒ Object

Returns the value of attribute num_tires.



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# File 'lib/driving_physics/car.rb', line 7

def num_tires
  @num_tires
end

#powertrain ⇒ Object (readonly)

Returns the value of attribute powertrain.



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# File 'lib/driving_physics/car.rb', line 6

def powertrain
  @powertrain
end

#tire ⇒ Object (readonly)

Returns the value of attribute tire.



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# File 'lib/driving_physics/car.rb', line 6

def tire
  @tire
end

Instance Method Details

#air_force(speed) ⇒ Object

force opposing speed



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# File 'lib/driving_physics/car.rb', line 42

def air_force(speed)
  -0.5 * @frontal_area * @cd * @env.air_density * speed ** 2
end

#corner_mass ⇒ Object 



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# File 'lib/driving_physics/car.rb', line 105

def corner_mass
  self.total_mass / @num_tires
end

#drive_force(rpm) ⇒ Object 



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# File 'lib/driving_physics/car.rb', line 89

def drive_force(rpm)
  @tire.force(@powertrain.axle_torque(rpm))
end

#gear ⇒ Object 



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# File 'lib/driving_physics/car.rb', line 29

def gear
  @powertrain.gearbox.gear
end

#gear=(val) ⇒ Object 



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# File 'lib/driving_physics/car.rb', line 33

def gear=(val)
  @powertrain.gearbox.gear = val
end

#motor_rpm(tire_speed) ⇒ Object 



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# File 'lib/driving_physics/car.rb', line 97

def motor_rpm(tire_speed)
  @powertrain.gearbox.crank_rpm(tire_speed / @tire_radius)
end

#normal_force ⇒ Object

per tire



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# File 'lib/driving_physics/car.rb', line 110

def normal_force
  self.corner_mass * @env.g
end

#throttle ⇒ Object 



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# File 'lib/driving_physics/car.rb', line 21

def throttle
  @powertrain.motor.throttle
end

#throttle=(val) ⇒ Object 



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# File 'lib/driving_physics/car.rb', line 25

def throttle=(val)
  @powertrain.motor.throttle = val
end

#tire_inertial_force(force) ⇒ Object

force of opposite sign to force



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# File 'lib/driving_physics/car.rb', line 61

def tire_inertial_force(force)
  mag = force.abs
  sign = force / mag
  force_loss = 0
  5.times {
    # use magnitude, so we are subtracting only positive numbers
    acc = DrivingPhysics.acc(mag - force_loss, self.total_mass)
    alpha = acc / @tire.radius
    # this will be a positive number
    force_loss = @num_tires * @tire.implied_torque(alpha) /
                 @tire.radius
  }
  # oppose initial force
  -1 * sign * force_loss
end

#tire_rolling_force(omega) ⇒ Object

force of opposite sign to omega



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# File 'lib/driving_physics/car.rb', line 47

def tire_rolling_force(omega)
  @num_tires *
    @tire.rolling_friction(omega, normal_force: self.normal_force) /
    @tire.radius
end

#tire_rotational_force(omega) ⇒ Object

force of opposite sign to omega



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# File 'lib/driving_physics/car.rb', line 54

def tire_rotational_force(omega)
  @num_tires *
    @tire.rotating_friction(omega, normal_force: self.normal_force) /
    @tire.radius
end

#tire_speed(rpm) ⇒ Object 



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# File 'lib/driving_physics/car.rb', line 93

def tire_speed(rpm)
  @tire.tangential(@powertrain.axle_omega(rpm))
end

#tire_traction ⇒ Object

per tire



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# File 'lib/driving_physics/car.rb', line 115

def tire_traction
  @tire.traction(self.normal_force)
end

#to_s ⇒ Object 



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# File 'lib/driving_physics/car.rb', line 77

def to_s
  [[format("Mass: %.1f kg", self.total_mass),
    format("Fr.A: %.2f m^2", @frontal_area),
    format("cD: %.2f", @cd),
   ].join(' | '),
   format("POWERTRAIN:\n%s", @powertrain),
   format("Tires: %s", @tire),
   format("Corner mass: %.1f kg | Normal force: %.1f N",
          self.corner_mass, self.normal_force),
  ].join("\n")
end

#top_gear ⇒ Object 



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# File 'lib/driving_physics/car.rb', line 37

def top_gear
  @powertrain.gearbox.top_gear
end

#total_mass ⇒ Object 



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# File 'lib/driving_physics/car.rb', line 101

def total_mass
  @body_mass + @powertrain.mass + @tire.mass * @num_tires
end

#total_normal_force ⇒ Object 



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# File 'lib/driving_physics/car.rb', line 119

def total_normal_force
  self.total_mass * env.g
end