Abstract:In the case of linear systems, control law design is often performed so that the resulting closed-loop meets specific frequency requirements. However, in many cases, it may be observed that the obtained controller does not enforce timedomain requirements amongst which the objective of keeping an output variable in a given interval. In this article, a transformation is proposed to convert expected bounds on an output variable into time-varying saturations on the synthesized linear control law. It is demonstrate… Show more
“…Goodwin and de Dona (2004), Glattfelder and Schaufelberger (2003), a popular idea consists of modifying a nominal controller whenever the constraints are about to be violated. Following this line, the Output to Input Saturation Transformation (OIST) approach was recently proposed in Burlion (2012); Chambon, Burlion, and Apkarian (2015a) to replace the state constraints by some state-dependent control saturations. Such an approach is attractive because it enables use of the vast literature on control saturation problems and may especially lead to consider anti-windup loops which are now well understood (see e.g Galeani, Tarbouriech, Turner, and Zaccarian (2009); Tarbouriech and Turner (2009)).…”
In this paper, a new technique is proposed for trajectory tracking of a flexible spacecraft subject to angular velocity constraints. The problem is addressed using an Output to Input Saturation Transformation (OIST) which converts the prescribed bounds into state-dependent saturations on the control input signals. It is shown that an interval observer can be used in combination with the OIST technique to ensure that the constraints remain satisfied despite unmeasured flexible modes and torque disturbances. Some realistic simulations conclude the paper and validate our approach.
“…Goodwin and de Dona (2004), Glattfelder and Schaufelberger (2003), a popular idea consists of modifying a nominal controller whenever the constraints are about to be violated. Following this line, the Output to Input Saturation Transformation (OIST) approach was recently proposed in Burlion (2012); Chambon, Burlion, and Apkarian (2015a) to replace the state constraints by some state-dependent control saturations. Such an approach is attractive because it enables use of the vast literature on control saturation problems and may especially lead to consider anti-windup loops which are now well understood (see e.g Galeani, Tarbouriech, Turner, and Zaccarian (2009); Tarbouriech and Turner (2009)).…”
In this paper, a new technique is proposed for trajectory tracking of a flexible spacecraft subject to angular velocity constraints. The problem is addressed using an Output to Input Saturation Transformation (OIST) which converts the prescribed bounds into state-dependent saturations on the control input signals. It is shown that an interval observer can be used in combination with the OIST technique to ensure that the constraints remain satisfied despite unmeasured flexible modes and torque disturbances. Some realistic simulations conclude the paper and validate our approach.
“…Using this method along with some assumptions, it is possible to obtain guarantees on the fulfilment of the time-domain constraints when an unsatisfactory control law has already been designed. This article is an extension of the work presented in Chambon, Burlion, and Apkarian (2015a). It gives a comprehensive description of the method for minimum-phase linear systems with unknown finite-energy bounded disturbances.…”
For linear systems, the control law design is often performed so that the resulting closed-loop meets specific frequency-domain requirements. However, in many cases, it may be observed that the obtained controller does not enforce time-domain requirements amongst which the objective of keeping an output variable in a given interval. In this article, a transformation is proposed to convert prescribed bounds on an output variable into time-varying saturations on the synthesized linear control law. This transformation uses some well-chosen time-varying coefficients so that the resulting time-varying saturations do not overlap in the presence of disturbances. Using an anti-windup approach, it is demonstrated that the origin of the resulting closed-loop is globally asymptotically stable and that the regulated variable satisfies the time-domain constraints in the presence of an unknown finite-energy bounded disturbance. An application to a linear ball and beam model is presented.
“…For instance, the anti-windup framework [13], [14] can be applied in combination with the OIST technique (see e.g. [15]). In this paper, we propose to show how the OIST technique can be applied to the problem of UAV obstacle avoidance.…”
This paper presents a novel obstacle avoidance scheme for UAVs. This scheme is based on the use of a technique recently developed by one of the authors, which is based on a transformation of a variable constraint into an input saturation. In the case of obstacle avoidance, this saturation is designed so as to ensure a safe trajectory around the obstacles, offering a proof of this desired behavior. A low-cost RGB-D sensor has been used to detect obstacles as its output measurements of the environment are effortlessly interpreted even with a low power embedded processor. Experimental results are provided, together with a simulation, to prove the efficiency of the approach.
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