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Tests

All tests can be executed using the command:

include("examples/menu.jl")

Most of these tests are not yet unit tests.

Requirements

  1. the force must never be below zero.
  2. the max force shall not be above the nominal force of the winch, in this case 4000 N.
  3. the absolute value of the acceleration must never exceed max_acc.
  4. the oscillations after switching the active controller shall be low.
  5. the maximum of the force error shall be low
  6. the mean of the square of the speed error shall be low
  7. the robustness for model errors (for example with respect to the inertia of the drum and the drum diameter) shall be high

Open question: can all these requirements be combined in two or three performance indicators, fornexample efficiency, robustness and damage? See also: Performance Indicators

SpeedController

SpeedController1

This test assumes a wind speed that starts at zero and reaches its nominal value after 0.25s. The nominal value is a triangle signal between 4 and 8 m/s and a period time of 4s. The tether direction is aligned with the wind direction, the set value for the reel-out speed is 4 m/s. This means when the nominal reel-out speed is reached, the apparent wind speed is between zero and 4 m/s. The force is proportional to the square of $v_a$.

test_speedcontroller1

SpeedController2

This test is similar to the last test, but the set speed is calculated according to $v_{ro} = \sqrt{f} * kv$ , where $f$ is the measured tether force and $kv$ is a constant that needs to be optimized for a given kite power system. This should allow optimal energy harvesting during reel-out.

test_speedcontroller1

ForceSpeedController

ForceSpeedController1

This controller tests the combination of the lower force controller with the speed controller for the reel-out phase, where the reel-out speed shall be proportional to the square-root of the force. The lower force limit was set to $1500~N$.

test_forcespeedcontroller1

State

0. lower force controller active; 1. speed controller active

ForceSpeedController2

This controller tests all controllers. The lower force limit was set to $350~N$, the upper force limit to $3800~N$. test_forcespeedcontroller1

State

0. lower force controller active; 1. speed controller active; 2. upper force controller active

The results after autotuning can be found here: Example result

Ideas

  • add torque controlled winch (which will require a modified controller)
  • add static tether model
  • linearize the winch+tether models
  • create bode plots
  • analyze the stability