Model and Detect Drivetrain Faults

R2026b

This example shows how to detect and respond to a fault in a drivetrain using a Rotational Damper block. The Rotational Damper block allows you to specify the damping coefficient as a function of temporal or behavioral triggers. You can program the damping coefficient to change at a particular time in the simulation or when the number of shocks for a given acceleration exceeds a limit to model fault behavior. Fault modeling allows you to predict how your actual physical system responds when it experiences real faults. It also allows you to test the robustness and responsiveness of your control system.

In the example, the fault is detected by a damper that is attached to a flexible shaft. Although you can perform most of the steps in this example using the tools that the Simulink® and Simscape™ Driveline™ user interfaces provide, scripts are supplied. You can combine the scripts into a larger script for parameter sweeps.

  1. Open the model. At the MATLAB® command prompt, enter:

    openExample('sdl/ShaftWithTorsionalFlexibilityExample')
model = 'ShaftWithTorsionalFlexibility';

    This model contains two flexible aluminum shafts modeled using a lumped parameter approach. A motor drives the motor shaft. A viscous damper is connected to the load shaft. The viscous damper is represented by a Rotational Damper block from the Simscape > Foundation Library > Mechanical > Rotational Elements library. The Foundation Library Rotational Damper block is not able to detect or respond to faults.

  2. Simulate the model and plot the results.

    %% Simulate Model
sim(model)

%% Get simulation results
simlog01 = simlog_ShaftWithTorsionalFlexibility;
simlog_t = simlog01.Clutch.P.series.time;
simlog_pClutch = simlog01.Clutch.P.series.values('Pa');
simlog_wMotor = simlog01.Shaft_Motor.F.w.series.values('rad/s');
simlog_wLoad = simlog01.Shaft_Load.F.w.series.values('rad/s');

%% Plot results
X1 = simlog_t;
YMatrix1 = [simlog_wMotor simlog_wLoad];
Y1 = simlog_pClutch;

% Create figure
figure1 = figure('Name','ShaftWithTorsionalFlexibility',...
    'OuterPosition',[107 336 733 822]);

% Create axes
axes1 = axes('Parent',figure1,...
    'Position',[0.13 0.709 0.775 0.216]);
hold(axes1,'on');

% Activate the left side of the axes
yyaxis(axes1,'left');

% Create multiple lines using matrix input to plot
plot1 = plot(X1,YMatrix1,'LineWidth',2);
set(plot1(1),'DisplayName','Motor Shaft', 'Color', 'k');
set(plot1(2),'DisplayName','Load Shaft', 'Color', 'b');

% Create ylabel
ylabel('Speed (rad/s)');

% Comment/uncomment the following line to remove/
%  preserve the Y-limits of the axes
ylim(axes1,[-100 250]);

% Set the remaining axes properties
set(axes1,'YColor',[0 0.447 0.741]);

% Activate the right side of the axes
yyaxis(axes1,'right');

% Create plot
plot(X1,Y1,'DisplayName','Clutch Pressure','LineWidth',2, 'Color', 'r');

% Create ylabel
ylabel('Pressure (Pa)');

% Comment/uncomment the following line to remove/
%  preserve the Y-limits of the axes
ylim(axes1,[0 2000000]);

% Set the remaining axes properties
set(axes1,'YColor',[0.85 0.325 0.098]);
% Create xlabel
xlabel('Time (s)');

% Create title
title('Shaft Speeds and Clutch Pressure');

% Uncomment the following line to preserve the X-limits of the axes
% xlim(axes1,[0 0.2);

% Set the remaining axes properties
set(axes1,'LineStyleOrderIndex',2);
box(axes1,'on');
grid(axes1,'on');

% Create legend
legend1 = legend(axes1,'show');
% set(legend1,'Location','best');
set(legend1,...
    'Position',[0.6944 0.9125 0.1982 0.07270]);

    At the start of the simulation, the clutch is unlocked and the driven shaft is free. The initial velocity of the motor shaft is the specified 200 rad/s and the system starts at steady state. The oscillations triggered by the engaging and disengaging of the clutch are due to the flexibility in the shafts.

  3. Replace the Simscape damper with the Simscape Driveline Rotational Damper, which is in the Simscape > Driveline > Couplings & Drives > Springs & Dampers library. Label the new block Faultable Damper.

    %% Replace Rotational Damper from Foundation Library with
%  Faultable Rotational Damper from the Simscape Driveline Library

% Define Unfaultable Damper Block 
foundationDamper = [model,'/Damping Bearing'];

% Get Unfaultable Damper Block Damping Coefficient
dampingCoefficient = get_param(foundationDamper,'D');

% Get Unfaultable Damper Block Position
damperPosition = get_param(foundationDamper, 'Position');

% Delete Unfaultable Damper Block
delete_block(foundationDamper)

% Add Faultable Damper Block
faultableDamperLib = ...
    'sdl_lib/Couplings & Drives/Springs & Dampers/Rotational Damper';
faultableDamperPath = [model,'/Faultable Damper'];
add_block(faultableDamperLib,faultableDamperPath,...
    'Position',damperPosition,...
    'NamePlacement', 'alternate',...
    'D',dampingCoefficient)

  4. Enable a time-based fault and specify a response that includes a change in the damping coefficient and the generation of a MATLAB warning. Use these values for the damper Fault parameters:

    • Enable faults — Enabled

    • Faulted damping coefficient — 10

    • Enable temporal fault trigger — Enabled

    • Simulation time for fault event — 0.06

    • Reporting when fault occurs — Warning

    %% Define Faultable Damper Block Parameters
underDamp = '10';
overDamp = '150';

faultTime = '.06';

aMaxDef = '100';
aMaxHigh = '400';
aMaxLow = '50';

shockNMaxDef = '1';
shockNMaxHigh = '5';
shockNMaxLow = '2';

disabled = '0';
enabled = '1';

none = '1';
warning = '2';
error = '3';

%% Parameterize a Timed Fault
set_param(faultableDamperPath,...
     'enable_faults', enabled,...       % Enable faults
     'b_fault', underDamp,...           % Faulted damping coefficient 
     'temporal_fault', enabled,...      % Enable temporal fault trigger
     'fault_time', faultTime,....       % Simulation time for fault event
     'shock_fault', disabled,...        % Disable behavioral fault trigger
     'acceleration_limit', aMaxDef,...  % Maximum permissible acceleration
     'shock_limit', shockNMaxDef ,...   % Maximum number of shocks
     'report_fault', warning)           % Reporting when fault occurs

  5. Simulate the model and plot the results.

    %% Simulate
sim(model)

%% Get Simulation Results
simlog02 = simlog_ShaftWithTorsionalFlexibility;
simlog_t02 = simlog02.Clutch.P.series.time;
simlog_pClutch02 = simlog02.Clutch.P.series.values('Pa');
simlog_wMotor02 = simlog02.Shaft_Motor.F.w.series.values('rad/s');
simlog_wLoad02 = simlog02.Shaft_Load.F.w.series.values('rad/s');

%% Plot Results
X2 = simlog_t02;
YMatrix2 = [simlog_wMotor02 simlog_wLoad02];
Y2 = simlog_pClutch02;

% Create axes
axes2 = axes('Parent',figure1,...
    'Position',[0.125 0.4 0.775 0.216]);
hold(axes2,'on');

% Activate the left side of the axes
yyaxis(axes2,'left');

% Create multiple lines using matrix input to plot
plot1 = plot(X2,YMatrix2,'LineWidth',2);
set(plot1(1),'DisplayName','Motor Shaft', 'Color', 'k');
set(plot1(2),'DisplayName','Load Shaft', 'Color', 'b');

% Create ylabel
ylabel('Speed (rad/s)');

% Comment/uncomment the following line to remove/
%  preserve the Y-limits of the axes
ylim(axes2,[-100 250]);

% Set the remaining axes properties
set(axes2,'YColor',[0 0.447 0.741]);

% Activate the right side of the axes
yyaxis(axes2,'right');
% Create plot
plot(X2,Y2,'DisplayName','Clutch Pressure','LineWidth',2, 'Color', 'r');

% Create ylabel
ylabel('Pressure (Pa)');

% Comment/uncomment the following line to remove/
%  preserve the Y-limits of the axes
ylim(axes2,[0 2000000]);

% Set the remaining axes properties
set(axes2,'YColor',[0.85 0.325 0.098]);

% Create title
title('Time-Faulted Speeds and Clutch Pressure');

% Create xlabel
xlabel('Time (s)');

% Uncomment the following line to 
% preserve the X-limits of the axes
% xlim(axes1,[0 0.2]);

% Set the remaining axes properties
box(axes2,'on');
grid(axes2,'on');
set(axes2,'LineStyleOrderIndex',2);


    Warning: At time 0.060000, one or more assertions are triggered.
A fault event has occurred The assertion comes from:
Block path: ShaftWithTorsionalFlexibility/Faultable Damper
Assert location: (location information is protected)

    At simulation time t = 0.06 s, the time specified for the fault, a warning is reported. The damping coefficient drops and slows the speed of both shafts.

  6. Enable a shock-based fault and specify a response that includes a change in the damping coefficient and the generation of a MATLAB warning. Then, simulate the model and plot the new results. Use these values for the damper Fault parameters:

    • Enable faults — Yes

    • Faulted damping coefficient — 150

    • Enable temporal fault trigger — Disabled

    • Enable behavioral fault trigger — Enabled

    • Maximum permissible acceleration — 50

    • Maximum number of shocks — 2

    • Reporting when fault occurs — Warning

    %% Paramaterize a Shock Fault
set_param(faultableDamperPath,...
     'enable_faults', enabled,...       % Enable faults
     'b_fault', overDamp,...           % Faulted damping coefficient 
     'temporal_fault', disabled,...     % Disable temporal fault trigger
     'fault_time', faultTime,....       % Simulation time for fault event
     'shock_fault', enabled,...         % Enable behavioral fault trigger
     'acceleration_limit', aMaxHigh,...  % Maximum permissible acceleration
     'shock_limit', shockNMaxLow ,...   % Maximum number of shocks
     'report_fault', warning)           % Reporting when fault occurs

  7. Simulate the model and plot the results.

    %% Simulate
sim(model)

%% Get Simulation Results
simlog03 = simlog_ShaftWithTorsionalFlexibility;
simlog_t03 = simlog03.Clutch.P.series.time;
simlog_pClutch03 = simlog03.Clutch.P.series.values('Pa');
simlog_wMotor03 = simlog03.Shaft_Motor.F.w.series.values('rad/s');
simlog_wLoad03 = simlog03.Shaft_Load.F.w.series.values('rad/s');
 
%% Plot Results
X3 = simlog_t03;
YMatrix3 = [simlog_wMotor03 simlog_wLoad03];
Y3 = simlog_pClutch03;

% Create axes
axes3 = axes('Parent',figure1,...
    'Position',[0.125 0.08 0.775 0.216]);
hold(axes3,'on');

% Activate the left side of the axes
yyaxis(axes3,'left');

% Create multiple lines using matrix input to plot
plot1 = plot(X3,YMatrix3,'LineWidth',2);
set(plot1(1),'DisplayName','Motor Shaft', 'Color', 'k');
set(plot1(2),'DisplayName','Load Shaft', 'Color', 'b');

% Create ylabel
ylabel('Speed (rad/s)');

% Comment/uncomment the following line to 
% remove/preserve the Y-limits of the axes
ylim(axes3,[-100 250]);

% Set the remaining axes properties
set(axes3,'YColor',[0 0.447 0.741]);

% Activate the right side of the axes
yyaxis(axes3,'right');

% Create plot
plot(X3,Y3,'DisplayName','Clutch Pressure','LineWidth',2, 'Color', 'r');

% Create ylabel
ylabel('Pressure (Pa)');

% Comment/uncomment the following line to 
% remove/preserve the Y-limits of the axes
ylim(axes3,[0 2000000]);

% Set the remaining axes properties
set(axes3,'YColor',[0.85 0.325 0.098]);

% Create title
title('Shock-Faulted Shaft Speeds and Clutch Pressure');

% Create xlabel
xlabel('Time (s)');

% Uncomment the following line to 
% preserve the X-limits of the axes
% xlim(axes1,[0 0.2);

% Set the remaining axes properties
box(axes3,'on');
grid(axes3,'on');
set(axes3,'LineStyleOrderIndex',2);


    Warning: At time 0.026048, one or more assertions are triggered.
A fault event has occurred The assertion comes from:
Block path: ShaftWithTorsionalFlexibility/Faultable Damper
Assert location: (location information is protected)

    At simulation time t = 0.026 s, the maximum number of shocks for the specified acceleration is reached. A warning is reported and the damping coefficient increases and slows the speed of both shafts.