Class: DrivingPhysics::Tire::Condition

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

Overview

treat attributes of this class as mutable

Defined Under Namespace

Classes: Destroyed, Error

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(temp_c: AIR_TEMP, tread_mm:, cords_mm:) ⇒ Condition

Returns a new instance of Condition.



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# File 'lib/driving_physics/tire.rb', line 143

def initialize(temp_c: AIR_TEMP, tread_mm:, cords_mm:)
  @tread_mm = tread_mm.to_f
  @cords_mm = cords_mm.to_f
  @temp_c = temp_c.to_f
  @heat_cycles = 0
  @hottest_temp = @temp_c
  @debug_temp = false
  @debug_wear = false
end

Instance Attribute Details

#cords_mm ⇒ Object

Returns the value of attribute cords_mm.



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# File 'lib/driving_physics/tire.rb', line 136

def cords_mm
  @cords_mm
end

#debug_temp ⇒ Object

Returns the value of attribute debug_temp.



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# File 'lib/driving_physics/tire.rb', line 136

def debug_temp
  @debug_temp
end

#debug_wear ⇒ Object

Returns the value of attribute debug_wear.



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# File 'lib/driving_physics/tire.rb', line 136

def debug_wear
  @debug_wear
end

#heat_cycles ⇒ Object

Returns the value of attribute heat_cycles.



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# File 'lib/driving_physics/tire.rb', line 136

def heat_cycles
  @heat_cycles
end

#temp_c ⇒ Object

Returns the value of attribute temp_c.



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# File 'lib/driving_physics/tire.rb', line 136

def temp_c
  @temp_c
end

#tread_mm ⇒ Object

Returns the value of attribute tread_mm.



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# File 'lib/driving_physics/tire.rb', line 136

def tread_mm
  @tread_mm
end

Instance Method Details

#temp_tick(ambient_temp:, g:, slide_speed:, mass:, tire_mass:, critical_temp:) ⇒ Object 



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# File 'lib/driving_physics/tire.rb', line 160

def temp_tick(ambient_temp:, g:, slide_speed:,
              mass:, tire_mass:, critical_temp:)
  # env:
  # * mass (kg) (e.g. 1000 kg)
  # * tire_mass (kg) (e.g. 10 kg)
  # * critical temp (c) (e.g. 100c)
  # * g (e.g. 1.0 g)
  # * slide_speed (m/s) (typically 0.1, up to 1 or 10 or 50)
  # * ambient_temp (c) (e.g. 30c)

  # g gives a target temp between 25 and 100
  # at 0g, tire tends to ambient temp
  # at 1g, tire tends to 100 c
  # that 100c upper target also gets adjusted due to ambient temps

  target_hot = critical_temp + 5
  ambient_diff = AIR_TEMP - ambient_temp
  target_hot -= (ambient_diff / 2)
  puts "target_hot=#{target_hot}" if @debug_temp

  if slide_speed <= 0.1
    target_g_temp = ambient_temp + (target_hot - ambient_temp) * g
  else
    target_g_temp = target_hot
  end
  puts "target_g_temp=#{target_g_temp}" if @debug_temp

  slide_factor = slide_speed * 5
  target_slide_temp = target_g_temp + slide_factor

  puts "target_slide_temp=#{target_slide_temp}" if @debug_temp

  # temp_tick is presumed to be +1.0 or -1.0 (100th of a degree)
  # more mass biases towards heat
  # more tire mass biases for smaller tick

  tick = @temp_c < target_slide_temp ? 1.0 : -1.0
  tick += slide_speed / 10
  puts "base tick: #{tick}" if @debug_temp

  mass_factor = (mass - 1000).to_f / 1000
  if mass_factor < 0
    # lighter car cools quicker; heats slower
    tick += mass_factor
  else
    # heavier car cools slower, heats quicker
    tick += mass_factor / 10
  end
  puts "mass tick: #{tick}" if @debug_temp

  tire_mass_factor = (tire_mass - 10).to_f / 10
  if tire_mass_factor < 0
    # lighter tire has bigger tick
    tick -= tire_mass_factor
  else
    # heavier tire has smaller tick
    tire_mass_factor = (tire_mass - 10).to_f / 100
    tick -= tire_mass_factor
  end
  puts "tire mass tick: #{tick}" if @debug_temp
  puts if @debug_temp

  tick
end

#tick!(ambient_temp:, g:, slide_speed:, mass:, tire_mass:, critical_temp:) ⇒ Object 



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# File 'lib/driving_physics/tire.rb', line 242

def tick!(ambient_temp:, g:, slide_speed:,
          mass:, tire_mass:, critical_temp:)

  # heat cycle:
  # when the tire goes above the critical temp and then
  # cools significantly below the critical temp
  # track @hottest_temp

  @temp_c += temp_tick(ambient_temp: ambient_temp,
                       g: g,
                       slide_speed: slide_speed,
                       mass: mass,
                       tire_mass: tire_mass,
                       critical_temp: critical_temp) / 100
  @hottest_temp = @temp_c if @temp_c > @hottest_temp
  if @hottest_temp > critical_temp and @temp_c < critical_temp * 0.8
    @heat_cycles += 1
    @hottest_temp = @temp_c
  end

  # a tire should last for 30 minutes at 1g sustained
  # with minimal sliding
  # 100 ticks / sec
  # 6000 ticks / min
  # 180_000 ticks / 30 min
  # 10mm = 180_000 ticks
  # wear_tick is nominally 1 / 18_000 mm

  wt = wear_tick(g: g,
                 slide_speed: slide_speed,
                 mass: mass,
                 critical_temp: critical_temp)

  if @tread_mm > 0
    @tread_mm -= wt / 18000
    @tread_mm = 0 if @tread_mm < 0
  else
    # cords wear 2x faster
    @cords_mm -= wt * 2 / 18000
    if @cords_mm <= 0
      raise(Destroyed, "no more cords")
    end
  end
end

#to_s ⇒ Object 



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# File 'lib/driving_physics/tire.rb', line 153

def to_s
  [format("Temp: %.1f C", @temp_c),
   format("Tread: %.2f (%.1f) mm", @tread_mm, @cords_mm),
   format("Cycles: %d", @heat_cycles),
  ].join(' | ')
end

#wear_tick(g:, slide_speed:, mass:, critical_temp:) ⇒ Object 



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# File 'lib/driving_physics/tire.rb', line 225

def wear_tick(g:, slide_speed:, mass:, critical_temp:)
  # cold tires wear less
  tick = [0, @temp_c.to_f / critical_temp].max
  puts "wear tick: #{tick}" if @debug_wear

  # lower gs reduce wear in the absence of sliding
  tick *= g if slide_speed <= 0.1
  puts "g wear tick: #{tick}" if @debug_wear

  # slide wear
  tick += slide_speed
  puts "slide wear tick: #{tick}" if @debug_wear
  puts if @debug_wear
  tick
end