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Safety needs to be guaranteed before we can introduce robots into our working environments. For a biped robot to navigate safely in a crowd it must maintain balance and avoid collisions. In highly dynamic and unpredictable environments like crowds, collision avoidance is usually interpreted as passive safety, i.e. that the robot can stop before any collision occurs. We show that both balance preservation...
In this paper, we present a Nonlinear Model Predictive Control scheme, which is able to generate walking motions in multi-contact situations. Walking up and down stairs with an additional hand support is a typical example, which we address in simulation. Computing such a nonlinear control scheme is usually done with a Newton method, a potentially time-consuming procedure involving iterative linearizations...
A novel approach to minimum-time control is presented. It is stated in terms of a hierarchical optimization problem, which is standard in the field of robotics. This is advantageous as already existing tools can be used to approach its solution. Our formulation is applied to the online generation of trajectories for industrial robots performing pick and place operations in the presence of obstacles...
A crucial part in biped walking motion generation is to ensure dynamic feasibility, which takes the form of a nonlinear constraint in the general case. Our proposition is to bound the nonlinear part of the dynamic feasibility constraint between some properly chosen extreme values. Making sure that this constraint is satisfied for the extreme values guarantees its satisfaction for all possible values...
Humanoid robots propel themselves and perform tasks by interacting with their environment through contact forces. Typically, nonuniqueness of these forces is dealt with by distributing them evenly between the contacts. In the present paper, we introduce strict prioritization in contact force distribution, to reflect situations when an application of certain contact forces should be avoided as much...
The standard approach to real-time control of humanoid robots relies on approximate models to produce a motion plan, which is then used to control the whole body. Separation of the planning stage from the controller makes it difficult to account for the whole body motion objectives and constraints in the plan. For this reason, we propose to omit the planning stage and introduce long-term balance constraints...
The combination of task and motion planning presents us with a new problem that we call geometric backtracking. This problem arises from the fact that a single symbolic state or action may be geometrically instantiated in infinitely many ways. When a symbolic action cannot be geometrically validated, we may need to backtrack in the space of geometric configurations, which greatly increases the complexity...
Coordinating multiple autonomous ground vehicles is paramount to many industrial applications. Vehicle trajectories must take into account temporal and spatial requirements, e.g., usage of floor space and deadlines on task execution. In this paper we present an approach to obtain sets of alternative execution patterns (called trajectory envelopes) which satisfy these requirements and are conflict-free...
The synthesis and evaluation of multi-fingered grasps on complex objects is a challenging problem that has received much attention in the robotics community. Although several promising approaches have been developed, applications to real-world systems are limited to simple objects or gripper configurations. The paradigm of Independent Contact Regions (ICRs) has been proposed as a way to increase the...
The synthesis of multi-fingered grasps on nontrivial objects requires a realistic representation of the contact between the fingers of a robotic hand and an object. In this work, we use a patch contact model to approximate the contact between a rigid object and a deformable anthropomorphic finger. This contact model is utilized in the computation of Independent Contact Regions (ICRs) that have been...
Two different synthesis routes, in particular deposition-precipitation (DP) and modified deposition-precipitation (MDP) have been used for preparation of gold/ceria catalysts. The catalysts have exhibited significant differences in CO, CH3OH and (CH3)2O oxidation. The most pronounced effect of different preparation methods was registered in the CO oxidation reaction. DP-prepared catalyst showed high...
The Heston stochastic volatility model is one of the most popular models for the evolution of stocks and futures prices, which includes a stochastic process for the volatility. In practice it is usually enhanced by adding a Poisson jump process, which improves the overall correspondence with the observed behaviour of prices in the marketplace. The pricing of financial options by means of Monte Carlo...
This article presents a comparison between dense and sparse model predictive control (MPC) formulations, in the context of walking motion generation for humanoid robots. The former formulation leads to smaller, the latter one to larger but more structured optimization problem. We put an accent on the sparse formulation and point out a number of advantages that it presents. In particular, motion generation...
The concept of independent contact regions on a target object's surface, in order to compensate for shortcomings in the positioning accuracy of robotic grasping devices, is well known. However, the numbers and distributions of contact points forming such regions is not unique and depends on the underlying computational method. In this work we present a computation scheme allowing to prioritize contact...
This article presents a comparison between dense and sparse model predictive control (MPC) formulations, in the context of walking motion generation for humanoid robots. The former formulation leads to smaller, the latter one to larger but more structured optimization problem. We put an accent on the sparse formulation and point out a number of advantages that it presents. In particular, motion generation...
The concept of independent contact regions on a target object's surface, in order to compensate for shortcomings in the positioning accuracy of robotic grasping devices, is well known. However, the numbers and distributions of contact points forming such regions is not unique and depends on the underlying computational method. In this work we present a computation scheme allowing to prioritize contact...
The article presents an improved formulation of an existing model predictive control scheme used to generate online “stable” walking motions for a humanoid robot. We introduce: (i) a change of variable that simplifies the optimization problem to be solved; (ii) a simply bounded formulation in the case when the positions of the feet are predetermined; (iii) a formulation allowing foot repositioning...
The paper presents simulation of the dynamics of a recently developed energy efficient permanent magnet electromagnetic valve actuator. The simulation is carried out using decoupled approach where the 3D magnetic field problem is solved separately from the electric circuit and mechanical motion problems. Finite element method with edge elements and ANSYS program are used for the magnetic field analysis...
This article introduces a new technique for planning reactionless paths to a point in Cartesian space, for manipulators mounted on a free-floating satellite. It is based on decomposition of the manipulator joint space into sets referred to as primitives which have redundancy one with respect to the attitude motion of the base body. The time duration of the manipulator motion is divided into sub-intervals...
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