diff options
Diffstat (limited to 'uav_params.m')
| -rw-r--r-- | uav_params.m | 109 |
1 files changed, 89 insertions, 20 deletions
diff --git a/uav_params.m b/uav_params.m index 7bed89c..da8a19b 100644 --- a/uav_params.m +++ b/uav_params.m @@ -1,6 +1,7 @@ % Retrieve or compute parameters for ducted-fan VTOL micro-UAV. % % Copyright (C) 2024, Naoki Sean Pross, ETH Zürich +% This work is distributed under a permissive license, see LICENSE.txt function [params] = uav_params() @@ -24,31 +25,49 @@ params.physics = struct(... % ------------------------------------------------------------------------ % Mechanical measurements +% Inertia marix at center of mass, +% numbers from CAD are in g * mm^2, convert to kg * m^2 +J = [ + 5.856E+08, 1.121E+06, -3.506E+05; + 1.121E+06, 4.222E+08, 6.643E+06; + -3.506E+05, 6.643E+06, 4.678E+08 +] * 1e-9; + +% Approximate propeller with a disk +m_prop = 200e-3; % mass of propeller +r_prop = 85e-3; % radius of propeller +J_prop = .5 * m_prop * r_prop^2; + params.mechanical = struct(... - 'Mass', 4.0, ... + 'Mass', 3.0, ... 'DuctRadius', 46e-3, ... 'DuctHeight', 171e-3, ... 'FlapZDistance', 98e-3, ... % flap distance along z from center of mass - 'InertiaTensor', 5e-3 * eye(3), ... % TODO true values, assume diagonal - 'GyroscopicInertiaZ', 0 ... % assume no gyroscopic effects for now + 'InertiaTensor', J, ... + 'GyroscopicInertiaZ', J_prop ... % assume small angle ); % ------------------------------------------------------------------------ % Actuator limits and measurements -% Cheap servos usually give a "speed" in seconds / 60 degrees without load -servo_speed = 0.19; % seconds per 60 deg -servo_angular_velocity = (pi / 3) / servo_speed; +% Servos usually give a "speed" in seconds / 60 degrees without load +servo_speed = 0.13; % seconds / 60 deg +servo_angular_velocity = (60 / servo_speed) * (pi / 180); % rad / s params.actuators = struct(... - 'TurbineMaxSpeed', 620.7, ... % in rad / s - 'ServoAbsMaxAngle', 25 * pi / 180, ... % in radians + 'PropellerMaxAngularVelocity', 620.7, ... % in rad / s + 'ServoAbsMaxAngle', 20 * pi / 180, ... % in radians + 'ServoMaxTorque', 4.3 * 1e-2, ... % in kg / m 'ServoNominalAngularVelocity', servo_angular_velocity ... ); +% IMU runs in NDOF mode params.measurements = struct(... - 'SensorFusionBandwidth', 1e3, ... - 'SensorFusionDelay', 8e-3 ... + 'SensorFusionDelay', 20e-3, ... % in s + 'LIDARAccuracy', 10e-3, ... % in m + 'LIDARMaxDistance', 40, ... % inm + 'LIDARBandwidth', 100, ... % in Hz for z position + 'IMUBandwidth', 100 ... % in Hz ); % ------------------------------------------------------------------------ @@ -57,23 +76,26 @@ params.measurements = struct(... % Compute thrust proportionality factor from actuator limits % from thrust relation F = k * omega^2. % FIXME: this is not ideal, need better measurements -omega_max = params.actuators.TurbineMaxSpeed; +omega_max = params.actuators.PropellerMaxAngularVelocity; F_max = 38.637; % in N (measured) -k_T = sqrt(F_max / omega_max); +k_T = F_max / omega_max^2; +% FIXME: LiftCoefficient comes from +% https://scienceworld.wolfram.com/physics/LiftCoefficient.html params.aerodynamics = struct(... 'ThrustOmegaProp', k_T, ... % in s^2 / (rad * N) - 'FlapArea', 23e-3 * 10e-3 * 1.5, ... % FIXME factor 150% was chosen at random - 'DragCoefficients', [1, 4] .* 1e-3, ... % TODO - 'LiftCoefficient', 1e-3 ... % TODO + 'FlapArea', 23e-3 * 10e-3, ... % in m^2 + 'DragCoefficients', [1, .1], ... % TODO + 'LiftCoefficient', 2 * pi ... % TODO ); + % ------------------------------------------------------------------------ % Linearization point of non-linear dynamics. % Compute theoretical thrust required to make the UAV hover % from the relation mg = k * omega^2 -% FIXME: This value should probably be replaced with a measurement +% FIXME: This value should probably be replaced with a measurement g = params.physics.Gravity; m = params.mechanical.Mass; k = params.aerodynamics.ThrustOmegaProp; @@ -81,9 +103,10 @@ k = params.aerodynamics.ThrustOmegaProp; omega_hover = sqrt(m * g / k); params.linearization = struct(... - 'Position', [0; 0; -3], ... % in inertial frame, z points down + 'PadeApproxOrder', 2, ... + 'Position', [0; 0; -2], ... % in inertial frame, z points down 'Velocity', [0; 0; 0], ... % in inertial frame - 'Angles', [0; 0; 0], ... % in body frame + 'Angles', [0; 0; pi / 4], ... % in body frame 'AngularVelocities', [0; 0; 0], ... % in body frame 'Inputs', [0; 0; 0; 0; omega_hover] ... % Flaps at rest and turbine at X ); @@ -92,9 +115,55 @@ params.linearization = struct(... % Performance requirements params.performance = struct(... - 'MaxHorizontalSpeed', 1e-2, ... % in m / s - 'MaxVerticalSpeed', 5e-2 ... % in m / s + 'ReferencePosMaxDistance', 1, ... % m + 'HorizontalPosMaxError', 2, ... % m + 'HorizontalMaxSpeed', 2, ... % m / s + 'HorizontalSettleTime', 6, ... % s + 'VerticalPosMaxError', 2, ... % m + 'VerticalMaxSpeed', 2, ... % m / s + 'VerticalSettleTime', 4, ... % s + 'AngleMaxPitchRoll', 10 * pi / 180, ... % in rad + 'AngleMaxYaw', pi, ... % rad + 'AngleMaxAngularRate', 20 * pi / 180 ... % rad / s ); +% Scaling matrices (because signals are normalized wrt parameter performance) +p = params.performance; + +params.ErrorScalingMatrix = blkdiag(... + eye(4) * params.actuators.ServoAbsMaxAngle, ... + params.actuators.PropellerMaxAngularVelocity ... + - params.linearization.Inputs(5), ... + eye(2) * p.HorizontalPosMaxError, ... + p.VerticalPosMaxError, ... + eye(2) * p.HorizontalMaxSpeed, ... + p.VerticalMaxSpeed, ... + eye(2) * p.AngleMaxPitchRoll, ... + p.AngleMaxYaw); + +params.OutputScalingMatrix = blkdiag(... + eye(2) * p.HorizontalPosMaxError, ... + p.VerticalPosMaxError, ... + eye(2) * p.HorizontalMaxSpeed, ... + p.VerticalMaxSpeed, ... + eye(2) * p.AngleMaxPitchRoll, ... + p.AngleMaxYaw, ... + eye(3) * p.AngleMaxAngularRate); + + +horiz_settle_speed = (1 - exp(-1)) / params.performance.HorizontalSettleTime; +if horiz_settle_speed > params.performance.HorizontalMaxSpeed + fprintf(['Contradictory performance requirements: ' ... + 'velocity needed to attain horizontal settle time is ' ... + 'higher than HorizontalMaxSpeed']); +end + +vert_settle_speed = (1 - exp(-1)) / params.performance.VerticalSettleTime; +if vert_settle_speed > params.performance.VerticalMaxSpeed + fprintf(['Contradictory performance requirements: ' ... + 'velocity needed to attain vertical settle time is ' ... + 'higher than VerticalMaxSpeed']); +end + end % vim: ts=2 sw=2 et: |