This paper presents a Center of Mass (CoM) based manipulation and regrasp planner that implements stability constraints to preserve the robot balance. The planner provides a graph of IK-feasible, collision-free and stable motion sequences, constructed using an energy based motion planning algorithm. It assures that the assembly motions are stable and prevent the robot from falling while performing dexterous tasks in different situations. Furthermore, the constraints are also used to perform an RRT-inspired task-related stability estimation in several simulations. The estimation can be used to select between single-arm and dual-arm regrasping configurations to achieve more stability and robustness for a given manipulation task. To validate the planner and the task-related stability estimations, several tests are performed in simulations and real-world experiments involving the HRP5P humanoid robot, the 5th generation of the HRP robot family. The experiment results suggest that the planner and the task-related stability estimation provide robust behavior for the humanoid robot while performing regrasp tasks.
The CoM constrained planner is an enhanced version of our previous planner @cite_24 , it builds a regrasp graph by connecting nodes between given initial and goal placements for an object, and searches the graph to find a sequence of pick-and-place sub-tasks. This generates a sequence of states, grasps, transit and transfer motion, connecting the starting and ending nodes. This paper improves the previous planner by evaluating if the state of the robot-object system is stable, in order to preserve its balance during searching. If the state is IK-unfeasible, generates a collision, or makes the robot fall out of balance, the corresponding node is removed and the search continues until a set of nodes connecting the initial and goal poses is found.
@cite_24
2036016432 1558116630 1584596462 2888726795
This paper presents a novel randomized motion planner for robots that must achieve a specified goal under kinematic and or dynamic motion constraints while avoiding collision with moving obstacles with known trajectories. The planner encodes the motion constraints on the robot with a control system and samples the robot's state × time space by picking control inputs at random and integrating its equations of motion. The result is a probabilistic roadmap of sampled state ×time points, called milestones, connected by short admissible trajectories. The planner does not precompute the roadmap; instead, for each planning query, it generates a new roadmap to connect an initial and a goal state×time point. The paper presents a detailed analysis of the planner's convergence rate. It shows that, if the state×time space satisfies a geometric property called expansiveness, then a slightly idealized version of our implemented planner is guaranteed to find a trajectory when one exists, with probability quickly converg... This paper presents a new geometrical formulation of the manipulation task planning problem in robotics. The problem is shown to be a constrained instance of the coordinated motion planning problem for multiple moving bodies. The constraints are related to the placement and the motion of objects, and can be expressed geometrically. We give a general paradigm for building Manipulation Task Planners based on the proposed formulation. A manipulation task appears as a path in the configuration space of the robot and all movable objects. A manipulation path is a sequence of constrained paths: transit-paths , where the robot moves "alone'', and transfer-paths , where the robot holds an object. The approach consists in building a Manipulation Graph that models the connectivity between certain regions in the global configuration space by transit-paths and transfer-paths. This approach is then applied to the case of a finite number of object placements and grasps. The nodes in the Manipulation Graph correspond to well identified configurations and the edges correspond to paths built from a series of configuration space slices. An implemented system is presented and discussed. This paper addresses the problem of finding robot configurations to grasp assembly parts during a sequence of collaborative assembly operations. We formulate the search for such configurations as a constraint satisfaction problem (CSP). Collision constraints in an operation and transfer constraints between operations determine the sets of feasible robot configurations. We show that solving the connected constraint graph with off-the-shelf CSP algorithms can quickly become infeasible even for a few sequential assembly operations. We present an algorithm which, through the assumption of feasible regrasps, divides the CSP into independent smaller problems that can be solved exponentially faster. The algorithm then uses local search techniques to improve this solution by removing a gradually increasing number of regrasps from the plan. The algorithm enables the user to stop the planner anytime and use the current best plan if the cost of removing regrasps from the plan exceeds the cost of executing those regrasps. We present simulation experiments to compare our algorithm's performance to a naive algorithm which directly solves the connected constraint graph. We also present a real robot system which uses the output of our planner to grasp and bring parts together in assembly configurations. We present a method enabling a robot to automatically arrange objects using task and motion planning. Given an input scene consisting of cluttered objects, our method first constructs a target layout of objects as a guidance to the robot for arranging them. For constructing the layout, we use positive examples and pre-extract hierarchical, spatial and pairwise relationships between objects, to understand the user preference on arranging objects. Our method then enables a robot to arrange input objects to reach their target configurations using any task and motion planner. To efficiently arrange the objects, we also propose a priority layer that decides an order of arranging objects to take a small amount of actions. This is achieved by utilizing a dependency graph between objects. We test our method in three different scenes with varying numbers of objects, and apply our method to two well-known task and motion planners with the virtual PR2 robot. We demonstrate that we can use the robot to automatically arrange objects, and show that our priority layer reduces the total running time up to 2.15 times in those tested planners.