This paper introduces a novel, lightweight method to solve the visibility problem for 2D grids. The proposed method evaluates the existence of lines-of-sight from a source point to all other grid cells in a single pass with no preprocessing and independently of the number and shape of obstacles. It has a compute and memory complexity of $\mathcal{O}(n)$, where n = nx×nyis the size of the grid, and requires at most ten arithmetic operations per grid cell. In the proposed approach, we use a linear first-order hyperbolic partial differential equation to transport the visibility quantity in all directions. In order to accomplish that, we use an entropy-satisfying upwind scheme that converges to the true visibility polygon as the step size goes to zero. This dynamic-programming approach allows the evaluation of visibility for an entire grid orders of magnitude faster than typical ray-casting algorithms. We provide a practical application of our proposed algorithm by posing the visibility quantity as a heuristic and implementing a deterministic, local-minima-free path planner, setting apart the proposed planner from traditional methods. Lastly, we provide necessary algorithms and an open-source implementation of the proposed methods.

This paper presents a robustified time-optimal motion planning approach for navigating an Autonomous Mobile Robot (AMR) from an initial state to a terminal state without colliding with obstacles, even when subjected to disturbances, which are modeled as random process noise and measurement noise. The approach iteratively solves the robustified problem by incorporating updated state-dependent safety margins for collision avoidance, the evolution of which is derived separately from the robustified problem. Additionally, a strategy for selecting an alternative terminal state to reach is introduced, which comes into play when the desired terminal state becomes infeasible considering the disturbances. Both of these contributions are integrated into a robustified motion planning and control pipeline, the efficacy of which is validated through simulation experiments.

Mechatronic application operating in dynamic and unstructured environment can benefit greatly from use of online optimization i.e. non-linear model predictive control (NLMPC). Unfortunately, the deterministic time implementation of NL-MPC on typical industrial automation hardware remains an open challenge, as well as guaranteeing performance in full operational behaviour. This article documents an implementation of an NL-MPC tool-chain. The developed methods are used on a highly dynamic parallel SCARA robot as a performant example that can benefit from the use of the proposed approach. Through us of NL-MPC, energy optimal path planning is demonstrated to operate robustly in all defined experimental conditions, while not violating the prescribed computational time. The resulting system performance is then benchmarked to the conventional industrial automation solution, and the improvement in performance is highlighted showing an improvement of up to 36% in energy efficiency.

We present Tasho (Task specification for receding horizon control), an open-source Python toolbox that facilitates systematic programming of optimal control problem (OCP)-based robot motion skills. Separation-of-concerns is followed while designing the components of a motion skill, which promotes their modularity and reusability. This allows us to program complex motion tasks by configuring and composing simpler tasks. We provide templates for several basic tasks like point-to-point and end-effector path-following tasks to speed up prototyping. Internally, the task's symbolic expressions are computed using CasADi and the resulting OCP is transcribed using Rockit. A wide and growing range of mature open-source optimization solvers are supported for solving the OCP. Monitor functions can be easily specified and are automatically deployed with the motion skill, so that the generated motion skills can be easily embedded in a larger control architecture involving higher-level discrete controllers. The motion skills thus programmed can be directly deployed on robot platforms using the C-code generation capabilities of CasADi. The toolbox has been validated through several experiments both in simulation and on physical robot systems. The open-source toolbox can be accessed at: https://gitlab.kuleuven.be/meco-software/tasho

Automated Guided Vehicles (AGVs) are a promising solution to automation in the view of Industry 4.0. The amount of goods that can be automatically transported can be further increased by efficient path planning and tracking methods. The efficiency is always a trade off in terms of cost, accuracy and flexibility, but should never influence safety. This paper proposes a flexible path planning and tracking solution, aiming to be applicable to several application domains, and which is able to dynamically avoid an (unforeseen) obstacle by an overtake manoeuvre. The approach is based on Model Predictive Control (MPC), consisting of multi-domain objectives, applicable to multiple vehicle models and is fast in calculation time due to an adjusted multiple shooting approach, which guarantees constraint satisfaction over the entire time domain. Further, a dynamic maximum velocity approach is proposed, which adapts the maximum velocity constraint to the environmental circumstances, such that an emergency brake can be applied if a human would appear behind a corner or obstacle. These algorithms are implemented on an autonomous forklift. The overall system performance is measured by the time-of-arrival of an obstacle avoidance manoeuvre. To evaluate the influence of usage of a low-cost ultra wideband (UWB) localization technology, the same algorithms and platforms are used in combination with standard off-the-shelf laser based localization technology. The UWB technology does lead to a slightly larger spread in terms of time-of-arrival, but is on average very much comparable to the laser-based setup.

This paper explores a combined global and local identification approach for linear parameter-varying systems. Ideally, the combined approach retains advantages of its two extremes - global and local - with the possibility to emphasize one or the other. Practically, it is prone to overfitting. This paper proposes a remedy based on the ℓ2,1-norm regularization, describes its implementation within the nonlinear least squares framework, and gives an experimental validation. The results show a substantial decrease in the Euclidean norm of the model parameters, which resulted in a significantly smoother frequency response function surface and in overall, less-deviating model behavior.