function [torque_tc, torque_engine, omega_engine] = engine_w_torque_converter (omega_tc)

% [TORQUE_TC, TORQUE_ENGINE, OMEGA_ENGINE] = ENGINE_W_TORQUE_CONVERTER (OMEGA_TC)
%   computes the torque converter torque, TORQUE_TC [Nm], as a function of
%   the  rotational velocity of the torque converter shaft and OMEGA [rad/s].
%   This model also computes the corresponding engine speed and torque.
%
%   INPUT:
%          omega_tc: speed at the output of the torque converter in rad/s
%   OUTPUT:
%          torque_tc: torque at the output of the torque conververter in Nm
%          torque_engine: torque at produced by the engine in Nm
%          omega_engine: speed of the engine in rad/s
%
%   Assumptions:
%     - Although qualitatively correct, this function is based entirely
%       on fictitious data.

%%
%% ME 2016
%% Fall 2007
%%
%% AUTHOR:  Chris Paredis
%%

% red-line RPM -- above this engine speed the fuel is cut off to avoid
% damage to the engine
omega_red = 6000*pi/30;

% make sure the input is within a valid range. The car should never operate
% at speeds outside this range, but it may happen that the ODE solver tries
% to make a big step and ends up at these velocities. This is just a
% saveguard to stop the root-finder from breaking.
if omega_tc < 0
    %warning('car should not move backwards');
    torque_tc = 0;
    torque_engine = 0;
    omega_engine = 0;
    fprintf('following output resulted from negative omega_tc: %g\n',omega_tc);
    return;
elseif omega_tc > 700
    omega_tc = 700;
end


% To compute the output torque for a given output velocity,
% start with some fairly tight bounds on the initial guess -- these bounds
% were determined through visual inspection of the solutions.  The code
% works with less specific bounds, but including these thight bounds
% improves the speed significantly.
upper_bound = omega_tc + 250*exp(-omega_tc/300);
lower_bound = max(30,omega_tc*0.9);
f = @(x)(torque_converter(x,omega_tc)-engine_model_CJP(x));
omega_engine = fzero(f, [lower_bound, upper_bound]);

% check whether we are beyond the red-line of the engine.  Clip the speed
% to the red-line
if omega_engine > omega_red
    omega_engine = omega_red;
end

% make one more call to the torque converter model to determine the output
% torque
[torque_engine,torque_tc] = torque_converter(omega_engine, omega_tc);