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Release Notes

2.07.22 - July 22 - 2022

  • Documentation update to the examples Modeling.

  • Added minor description in auxilary functions in /src/

  • Fem.m

    • Generated new mex files for the Local element computation. Now each matrix computation in during the fem simulation calls a .mex64 file. This significantly improves performance ~40% compare to .m files. During install, Sorotoki will ask to install the new mex files.

    • Added (proper) friction effects to the contact simulations. A good example is fem_bouncingball.m which initally started spinning due to improper implementation of the friction forces during contact. The interaction friction can be modified under Material.Cfr (default = 1e-6 for most sample materials). Added example to show the friction effects is: ./scripts/fem/2D/dynamics/fem_crawler.m

    • High interaction friction forces lead to instabilities, implement with caution. A fix will be issued later.
    • Added initial conditions to the dynamic Fem simulations. Now Fem.Utmpcan be overwritten before calling fem.simulate. This can be extremely handy if we like to simulate from a quasi-static equilbrium, e.g., gravity deflection. One can first call fem.solve(), get the displacement through U0 = fem.Log.U(end,:), then a new simulation: 
      fem.reset();
fem.set('Utmp',U0);
fem.simulate();
      We can also ensure there is no ramping of the gravity force by setting the following fem.set('GravityRamp',false);

  • Shapes.m

    • Major update to the class. Now, Shapes.reconstruct() will produce better POD bases from the finite element simulations. As example: 

      shp = Shapes(fem,Modal,'NNode',100,'L0',120,'FilterRadius',[15,15]);
shp = shp.reference([0,0],[119,0]);
shp = shp.reconstruct();
      This code will generate a basis from the data in Fem, and project its dynamics onto a curve spanned by the points: (0,0) -> (119,0). During the reconstruction, all system tensors are build accordingly.

    • Shapes.show() is implemented and will show the strain basis.

  • Model.m

    • Fixed a minus error in the gravitional force compuation that lead to incorrect orientation of the gravity vector.

2.05.19 - May 19 - 2022

  • Fem.m:
    • Addressed to solve Issue #7: Fixed issue with Fem.Log. If a nonlinear residual increment takes less than 2 iterations, data was not properly stored. To solve this, any nonlinear time increment must take at least two steps, as to ensure a new displacement field is introduced to the stress-strain calculations.

2.05.17 - May 17 - 2022

  • Added MEX compiler for Model, Gmodel, and Fem classes. This significantly improves the computation times of the Sorotoki toolkit. When calling sorotoki.m, the installer asks to compile the mex files. Note we do not support the original Matlab functions anymore, simple because of computational speed. Hence, the Matlab Coder Toolkit is a prerequisite for Sorotoki.
  • Updated verifySorotoki.m to include also Model.
  • Shapes
    • Updated the Fem -> Shapes converter that extracts the geometric modes from dynamic or quasi-static FEM data. This can be done using shp.Fem = Fem followed by shp.reconstruct, shp.rebuild. Then a dynamic model can be generated using mdl = Model(shp). We call this new strain basis the Geometry-Informed Variable Strain basis as the geometry of the soft robot is preserved into the functional basis.
    • Added Shapes.Material. Now hyper-elastic materials can be loaded into the stiffness and inertia tensor construction. The work is experimental since more research is required to properly include hyper-elastic materials into the Cosserat beam models.
  • Model
    • Added an auxiliary flow function to the Model class: dx = f(x,t). This can be used for integrator actions, like PI controllers. or adaptive controllers where unknown parameters evolutions can be included.

2.01.28 - Jan 28 - 2022

  • Improved stability of Newmark solver.

2.24.01 - Jan 24 - 2022

  • Fixed broken installer. vernum.m file was missing on Repo. It has been replaced with soropatch.m which also includes the patch notes.
  • @martijnschouten Missing DOI for citation, and long-term support/access.
  • Signed Distance Functions:
    • Added a new function Sdf.showcontour(). It will show the contour of 2D signed distance functions. Currently not implemented for 3D Sdfs.

2.13.01 - Jan 13 - 2022

  • Moved SOROTOKI from early alpha to alpha (prepping for official release).

  • Shapes.m:

    • Significant update to the class Shapes. Shapes now requests a Fem class , a Matlab function_handle of functionals, or a evaluated matrix of shape functions (); to construct the class. Then, it serves as an input for the class Model (e.g., dynamic modeling of soft robots), or as an Inverse Kinematic solver for beam models.
    • Added a function Shapes.jointEstimate(Fem). This will produce an optimal set of modal coefficient to reconstruct the beam model from FEM-driven data (accessed by Fem.Log).
    • Current Shapes.jointEstimate() exploits the fact that the shapes are orthonormal w.r.t. their integral over the spatial domain [0,L]. If shapes do not satisfy this conditions, inaccurate estimates can occur.
    • Added Y = gsog_poly(X) which ensure the columns of Y are mutually orthonormal derived from the matrix X. X must be full-rank. This function is simply the gramm-smith method for the innerproduct space int_C y_i y_j ds on the domain C := [0,L].

1.12.06 - Dec 6 - 2021

  • Fem.m:
    • Fixed some numerical issues with Fem.simulate() function. Stability is now further improved for larger timesteps.
    • Fixed some numerical issues with Fem.Contact. A wider range of TimeSteps result now in stable solutions. Still the timestep size should be taken with care. Also fixed the issues of induced (unstable) oscillations due to fast impact. Contact is now based on the initial Modulus of the hyper-elastic material,i.e., Material.Emod().
    • Added time-base function_handle for the external pressures in dynamic finite-element simulations. They can added using: Fem.AddConstraint('Pressure',id, @(t) sin(t));
    • Dynamic simulations now record the potential and kinetic energies.
    • Future implementation will have Load and Tendon-based dynamic forces
    • The potential energy of the external load is still missing...

1.12.02 - Dec 2 - 2021

  • Finite Elements:

    • Added Fem.simulate() function to the Nonlinear Finite Element. The function is a standard Newmark-Beta dynamic solver routine for NLFEM. Alternatively, fem.simulate() can be used as an alternative for fem.solve() by setting the Fem.Material.Zeta large (overdamped).
    • Fixed the stability issue of Fem.Contact. Contact can now be added with Fem.AddConstraint('Contact',@(x) sdf(x), [x,y]) (x and y move the SDF). for best stability, use Fem.simulate() with a TimeStep < 1/75.

  • Open issues:

    • Fem.simulate does not use dynamic external forces, rather the forces are scaled with a sigmoid function f_ext = f*sigmoid(t); This will be removed in the future with fext = @(t) f* .... - an explicit function of time that can be evaluated at time t.
    • Possible implementations: Displace, Load, Pressure, Gravity.

1.10.06 - Oct 6 - 2021

  • Added patch.md file to keep track of any changes to SOROTOKI.
  • Meshing:
    • Fixed an issue where Mesh.showSDF was not producing plots.

1.10.01 - Oct 1 - 2021

  • Official beta release of SOROTOKI