In this letter, we propose an approach to trajectory planning based on the purpose of the task. For a redundant manipulator, many end effector poses in the task space can be achieved with multiple joint configurations. In planning the motion, we are free to choose the configuration that is optimal for the particular task requirement. Many previous motion planning approaches have been proposed for the sole purpose of maximizing manipulability, or minimizing effort. However, there is a lack of formulation that is flexible enough to allow the designer to purposefully define the motion and force priority of the planned trajectory. Our approach exploits both velocity and force manipulability, depending on the purpose of the task. In this formulation, the purpose of the task is defined by the motion preference (“fast” or “strong”), which can be characterized by a direction of the desired motion, or force. These two directions can be used to evaluate the compatibility of a chosen configuration with the given task. We first demonstrate the possibility of generating two distinct motion plans by the kinematic alignment of desired velocity and force directions with the manipulator's velocity and force manipulability ellipses. Next, this configuration selection strategy is incorporated into a task-specific trajectory optimization formulation to generate dynamically feasible trajectories. Two distinct motions (force-oriented lifting motion and velocity-oriented ballistic motion) are planned. We also propose a blending method to generate a single motion plan that considers both force and velocity, each to a specified degree. Together the three motions (force, velocity, and blended) are successfully planned and executed on a three-link serial robotic manipulator. The letter concludes with discussion and future directions.

中文翻译：

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有目的的规划：特定于任务的轨迹优化

在这封信中，我们提出了一种基于任务目的的轨迹规划方法。对于冗余操纵器，任务空间中的许多末端执行器姿势可以通过多个关节配置来实现。在规划运动时，我们可以自由选择最适合特定任务要求的配置。许多先前的运动规划方法被提出的唯一目的是最大化可操作性或最小化努力。然而，缺乏足够灵活的公式来允许设计者有目的地定义计划轨迹的运动和力优先级。我们的方法根据任务的目的，利用速度和力的可操纵性。在此表述中，任务的目的由运动偏好（“快”或“强”）定义，其特征可以是所需运动或力的方向。这两个方向可用于评估所选配置与给定任务的兼容性。我们首先证明了通过将所需速度和力方向与操纵器的速度和力可操纵性椭圆进行运动学对齐来生成两个不同运动计划的可能性。接下来，这种配置选择策略被纳入特定于任务的轨迹优化公式中，以生成动态可行的轨迹。计划了两种不同的运动（力导向的提升运动和速度导向的弹道运动）。我们还提出了一种混合方法来生成单个运动计划，该计划在指定程度上考虑了力和速度。三种运动（力、速度和混合）一起在三连杆串行机器人操纵器上成功规划和执行。这封信最后进行了讨论和未来的方向。