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First solve for initial conditions failed to converge. Trying again with all high priorities relaxed to low.

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Pratik Shirude
Pratik Shirude on 6 Mar 2021
Answered: Steve Miller on 14 Mar 2021
Hi Guys,
I have made this powertrain for parallel hybrid configuration shown in picture below. when i run simulation i get get erros which are as follows
First solve for initial conditions failed to converge. Trying again with all high priorities relaxed to low.
Component:Simulink | Category:Model warning
Unable to satisfy all initial conditions. The variables involved are listed below. The following variables are involved in a constraint that conflicts with their targets: 'DC_Motor.w' (Angular velocity) 'Generic_Engine.engine_inertia.w' (Rotational velocity) Here are the equations involved: all components involved'Mini_tractor_powertrain/DC Motor'Equation location is: 'E:\toolbox\physmod\elec\library\m\+ee\+electromech\+brushed\dc_motor.sscp' (no line number info) 'Mini_tractor_powertrain/Generic Engine'Equation location is: 'E:\toolbox\physmod\simscape\library\m\+foundation\+mechanical\+rotational\inertia.ssc' (line 45) 'Mini_tractor_powertrain/Simple Gear'Equation location is: 'E:\toolbox\physmod\sdl\sdl\+sdl\+gears\simple_gear.sscp' (no line number info)
Component:Simulink | Category:Model warning
An error occurred while running the simulation and the simulation was terminated
Caused by:
If anybody has solution for this please reply immediately
  1 Comment
Bruno Rodriguez Esteban
Bruno Rodriguez Esteban on 8 Mar 2021
Hi Pratik,
Without the model, it is a bit difficult to debug, but the message indicates:
The following variables are involved in a constraint that conflicts with their targets: 'DC_Motor.w' (Angular velocity) 'Generic_Engine.engine_inertia.w' (Rotational velocity)
This means that the initial value of the angular velocity of the "DC_Motor" and "Generic_Engine" are different. You might be inputing contradictory values. They need to be consistent, otherwise the solver will struggle.
Hope this helps.
Regards,
Bruno.

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Answers (1)

Steve Miller
Steve Miller on 14 Mar 2021
Hi Pratik Shirude - here are three ways to eliminate the warnings at the start of the simulation.
  1. Remove the inertia from the Generic Engine block. On the "Dynamics" tab, set "Inertia" to "No Inertia".
  2. Put a flexible shaft between the engine and the motor (parallel spring-damper between the engine and the gear)
  3. Set the initial speed of the Generic Engine block to be exactly consistent with speed of the DC motor block, taking into account the gear ratio between the two blocks
The meaning of the diagnostic is as Bruno describes in his comment - you have specified two inconsistent initial shaft speeds in the Generic Engine and DC Motor block, and Simscape is trying to find a compromise between those two values. Since it is physically impossible to match both values, it is issuing a warning.
--Steve

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