Despite the classic nature of the problem, trajectory

tracking for soft robots, i.e. robots with compliant elements

deliberately introduced in their design, still presents several

challenges. One of these is to design controllers which can

obtain sufficiently high performance while preserving the physical

characteristics intrinsic to soft robots. Indeed, classic control

schemes using high gain feedback actions fundamentally alter the

natural compliance of soft robots effectively stiffening them, thus

**de facto **defeating their main design purpose. As an alternative

approach, we consider here to use a low-gain feedback, while

exploiting feedforward components. In order to cope with the

complexity and uncertainty of the dynamics, we adopt a decentralized,

iteratively learned feedforward action, combined with

a locally optimal feedback control. The relative authority of the

feedback and feedforward control actions adapts with the degree

of uncertainty of the learned component. The effectiveness of the

method is experimentally verified on several robotic structures

and working conditions, including unexpected interactions with

the environment, where preservation of softness is critical for

safety and robustness.

10aRobotics1 aAngelini, F.1 aDella Santina1 aGarabini, M.1 aBianchi, M.1 aGasparri, G M1 aGrioli, G.1 aCatalano, M. G.1 aBicchi, A. uhttp://www.centropiaggio.unipi.it/publications/decentralized-trajectory-tracking-control-soft-robots-interacting-environment.html01821nas a2200241 4500008004100000245015800041210006900199300001600268490000600284520098400290100001801274700001501292700001701307700001501324700001501339700001401354700002001368700001501388700001601403700001501419700001701434856012801451 2018 eng d00aEfficient Walking Gait Generation via Principal Component Representation of Optimal Trajectories: Application to a Planar Biped Robot With Elastic Joints0 aEfficient Walking Gait Generation via Principal Component Repres a2299–23060 v33 aRecently, the method of choice to exploit robot dynamics for efficient walking is numerical optimization (NO). The main drawback in NO is the computational complexity, which strongly affects the time demand of the solution. Several strategies can be used to make the optimization more treatable and to efficiently describe the solution set. In this letter, we present an algorithm to encode effective walking references, generated offline via numerical optimization, extracting a limited number of principal components and using them as a basis of optimal motions. By combining these components, a good approximation of the optimal gaits can be generated at run time. The advantages of the presented approach are discussed, and an extensive experimental validation is carried out on a planar legged robot with elastic joints. The biped thus controlled is able to start and stop walking on a treadmill, and to control its speed dynamically as the treadmill speed changes.

1 aGasparri, G M1 aManara, S.1 aCaporale, D.1 aAverta, G.1 aBonilla, M1 aMarino, H1 aCatalano, M. G.1 aGrioli, G.1 aBianchi, M.1 aBicchi, A.1 aGarabini, M. uhttp://www.centropiaggio.unipi.it/publications/efficient-walking-gait-generation-principal-component-representation-optimal00620nas a2200193 4500008003900000245005500039210005500094260006000149300001600209653001300225100001800238700001700256700001900273700001600292700002000308700001500328700001500343856006800358 2015 d00aVariable Stiffness Control for Oscillation Damping0 aVariable Stiffness Control for Oscillation Damping aHamburg, Germany, September 28 - October 02, 2015bIEEE a6543 - 655010aRobotics1 aGasparri, G M1 aGarabini, M.1 aPallottino, L.1 aMalagia, L.1 aCatalano, M. G.1 aGrioli, G.1 aBicchi, A. uhttp://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=735431200632nas a2200169 4500008003900000245008700039210006900126260002600195653001300221100001500234700001800249700001700267700001600284700001500300700001500315856013200330 2013 d00aSoft-Actuators in Cyclic Motion: Analytical Optimization of Stiffness and Pre-Load0 aSoftActuators in Cyclic Motion Analytical Optimization of Stiffn aAtlanta, Georgia, USA10aRobotics1 aVelasco, A1 aGasparri, G M1 aGarabini, M.1 aMalagia, L.1 aSalaris, P1 aBicchi, A. uhttp://www.centropiaggio.unipi.it/publications/soft-actuators-cyclic-motion-analytical-optimization-stiffness-and-pre-load.html