Change ChExternalDynamicsODE to an abstract class

src/chrono/physics/ChExternalDynamicsODE.cpp

@@ -43,10 +43,6 @@ void ChExternalDynamicsODE::Initialize() {
     }
 }
 
-ChExternalDynamicsODE* ChExternalDynamicsODE::Clone() const {
-    return new ChExternalDynamicsODE(*this);
-}
-
 ChVectorDynamic<> ChExternalDynamicsODE::GetInitialStates() {
     ChVectorDynamic<> y0(m_nstates);
     SetInitialConditions(y0);

src/chrono/physics/ChExternalDynamicsODE.h

@@ -25,16 +25,17 @@
 
 namespace chrono {
 
-/// Physics element that carries its own dynamics, described as a system of ODEs.
-/// The internal states are integrated simultaneously with the containing system and they can be accessed and used coupled
+/// Physics element that carries its own dynamics, described as an ODE IVP of the form:
+/// <pre>
+///   y' = f(t,y)
+///   y(t0) = y0
+/// </pre>
+/// The internal states are integrated simultaneously with the containing system and they can be accessed and coupled
 /// with other physics elements.
 class ChApi ChExternalDynamicsODE : public ChPhysicsItem {
   public:
     virtual ~ChExternalDynamicsODE();
 
-    /// "Virtual" copy constructor (covariant return type).
-    virtual ChExternalDynamicsODE* Clone() const override;
-
     /// Initialize the physics item.
     virtual void Initialize();
 
@@ -43,7 +44,7 @@ class ChApi ChExternalDynamicsODE : public ChPhysicsItem {
     virtual bool IsStiff() const { return false; }
 
     /// Get number of states (dimension of y).
-    virtual unsigned int GetNumStates() const { return 0; }
+    virtual unsigned int GetNumStates() const = 0;
 
     /// Get the initial values (state at initial time).
     ChVectorDynamic<> GetInitialStates();
@@ -59,14 +60,14 @@ class ChApi ChExternalDynamicsODE : public ChPhysicsItem {
 
     /// Set initial conditions.
     /// Must load y0 = y(0).
-    virtual void SetInitialConditions(ChVectorDynamic<>& y0) {}
+    virtual void SetInitialConditions(ChVectorDynamic<>& y0) = 0;
 
     /// Calculate and return the ODE right-hand side at the provided time and states.
     /// Must load rhs = f(t,y).
     virtual void CalculateRHS(double time,                 ///< current time
                               const ChVectorDynamic<>& y,  ///< current ODE states
                               ChVectorDynamic<>& rhs       ///< output ODE right-hand side vector
-    ) {}
+                              ) = 0;
 
     /// Calculate the Jacobian of the ODE right-hand side with respect to the ODE states.
     /// Must load J = df/dy.
@@ -81,6 +82,7 @@ class ChApi ChExternalDynamicsODE : public ChPhysicsItem {
         return false;
     }
 
+  protected:
     virtual void Update(double time, bool update_assets = true) override;
 
     virtual unsigned int GetNumCoordsPosLevel() override { return m_nstates; }
@@ -135,10 +137,10 @@ class ChApi ChExternalDynamicsODE : public ChPhysicsItem {
     virtual void VariablesQbIncrementPosition(double step) override;
     virtual void ConstraintsFbLoadForces(double factor = 1) override;
 
+  private:
     /// Compute the Jacobian at the current time and state.
     void ComputeJac(double time);
 
-  private:
     int m_nstates;                                ///< number of internal ODE states
     ChVectorDynamic<> m_states;                   ///< vector of internal ODE states
     ChVariablesGenericDiagonalMass* m_variables;  ///< carrier for internal dynamics states

src/chrono_fmi/ChExternalFmu.h

@@ -126,7 +126,7 @@ class ChApiFMI ChExternalFmu : public ChExternalDynamicsODE {
     void SetRealInputFunction(const std::string& name, std::function<double(double)> function);
 
     /// Initialize this physics item.
-    /// This function initializes the underlying FMU as well as this physcis item.
+    /// This function initializes the underlying FMU as well as this physics item.
     virtual void Initialize() override;
 
     /// Print the list of FMU variables.

src/demos/mbs/demo_MBS_external_ODE.cpp

@@ -42,6 +42,8 @@ class VanDerPolODE : public ChExternalDynamicsODE {
   public:
     VanDerPolODE(double mu) : m_mu(mu) {}
 
+    virtual VanDerPolODE* Clone() const override { return new VanDerPolODE(*this); }
+
     virtual unsigned int GetNumStates() const override { return 2; }
 
     virtual bool IsStiff() const override { return m_mu > 10; }