Andres Valenzuela | Massachusetts Institute of Technology (MIT) (original) (raw)

Papers by Andres Valenzuela

Research paper thumbnail of Whole-body motion planning with simple dynamics and full kinematics

Proceedings of the 14th IEEE-RAS International Conference on Humanoid Robots, 2014

To plan dynamic, whole-body motions for robots, one conventionally faces the choice between a com... more To plan dynamic, whole-body motions for robots, one conventionally faces the choice between a complex, fullbody dynamic model containing every link and actuator of the robot, or a highly simplified model of the robot as a point mass. In this paper we explore a powerful middle ground between these extremes. We present an approach to generate whole-body motions using a simple dynamics model, which enforces that the linear and angular momentum of the robot be consistent with the external wrenches on the robot, and a full-body kinematics model that enforces rich geometric constraints, such as end-effector positioning or collision avoidance. We obtain a trajectory for the robot and profiles of contact wrenches by solving a nonlinear optimization problem (NLP). We further demonstrate that we can plan without pre-specifying the contact sequence by exploiting the complementarity conditions between contact forces and contact distance. We demonstrate that this algorithm is capable of generating highly-dynamic motion plans with examples of a humanoid robot negotiating obstacle course elements and gait optimization for a quadrupedal robot.

Research paper thumbnail of An architecture for online affordance-based perception and whole-body planning

Journal of Field Robotics, Sep 2014

Research paper thumbnail of A summary of team MIT's approach to the virtual robotics challenge

Proceedings of the International Conference on Robotics and Automation (ICRA), May 2014

Research paper thumbnail of Optimally Scaled Hip-Force Planning: A control approach for quadrupedal running

This paper presents Optimally Scaled Hip-Force Planning (OSHP), a novel approach to controlling t... more This paper presents Optimally Scaled Hip-Force Planning (OSHP), a novel approach to controlling the body dynamics of running robots. Controllers based on OSHP form the high-level component of a hierarchical control scheme in which they direct lower level controllers, each responsible for coordinating the motion of a single leg. An OSHP controller takes in the state of the runner at

Research paper thumbnail of Bifurcations of optimal solutions for coordinated robotic systems: Numerical and homotopy methods

This paper presents the relatively rich and interesting bifurcation structure that is present in ... more This paper presents the relatively rich and interesting bifurcation structure that is present in the nature of optimal solutions to a multi-robot formation control problem. The problem considered is a two point nonlinear boundary-value problem that can only be solved numerically. Since common numerical solution techniques such as the shooting method are local in nature and hence are difficult to use to find multiple solutions, an alternative formulation of the problem is presented that can be solved through homotopy methods for polynomial systems. These methods are guaranteed to find all solutions within the resolution of the system description's discretization. Specifically, this paper studies a group of unicycle-like autonomous mobile robots operating in a 2-dimensional obstacle-free environment. Each robot has a predefined initial state and final state and the problem is to find the optimal path between two states for every robot. The path is optimized with respect to the control effort and the deviation from a desired formation. The bifurcation parameter is the relative weight given to penalizing the deviation from the desired formation versus control effort. It is shown that as this number varies, bifurcations of solutions are obtained. Considering the common use of optimization methods in robotic navigation and coordination problems, understanding the existence and structure of bifurcating and multiple solutions is of great importance in robotics.

Research paper thumbnail of Whole-body motion planning with simple dynamics and full kinematics

Proceedings of the 14th IEEE-RAS International Conference on Humanoid Robots, 2014

To plan dynamic, whole-body motions for robots, one conventionally faces the choice between a com... more To plan dynamic, whole-body motions for robots, one conventionally faces the choice between a complex, fullbody dynamic model containing every link and actuator of the robot, or a highly simplified model of the robot as a point mass. In this paper we explore a powerful middle ground between these extremes. We present an approach to generate whole-body motions using a simple dynamics model, which enforces that the linear and angular momentum of the robot be consistent with the external wrenches on the robot, and a full-body kinematics model that enforces rich geometric constraints, such as end-effector positioning or collision avoidance. We obtain a trajectory for the robot and profiles of contact wrenches by solving a nonlinear optimization problem (NLP). We further demonstrate that we can plan without pre-specifying the contact sequence by exploiting the complementarity conditions between contact forces and contact distance. We demonstrate that this algorithm is capable of generating highly-dynamic motion plans with examples of a humanoid robot negotiating obstacle course elements and gait optimization for a quadrupedal robot.

Research paper thumbnail of An architecture for online affordance-based perception and whole-body planning

Journal of Field Robotics, Sep 2014

Research paper thumbnail of A summary of team MIT's approach to the virtual robotics challenge

Proceedings of the International Conference on Robotics and Automation (ICRA), May 2014

Research paper thumbnail of Optimally Scaled Hip-Force Planning: A control approach for quadrupedal running

This paper presents Optimally Scaled Hip-Force Planning (OSHP), a novel approach to controlling t... more This paper presents Optimally Scaled Hip-Force Planning (OSHP), a novel approach to controlling the body dynamics of running robots. Controllers based on OSHP form the high-level component of a hierarchical control scheme in which they direct lower level controllers, each responsible for coordinating the motion of a single leg. An OSHP controller takes in the state of the runner at

Research paper thumbnail of Bifurcations of optimal solutions for coordinated robotic systems: Numerical and homotopy methods

This paper presents the relatively rich and interesting bifurcation structure that is present in ... more This paper presents the relatively rich and interesting bifurcation structure that is present in the nature of optimal solutions to a multi-robot formation control problem. The problem considered is a two point nonlinear boundary-value problem that can only be solved numerically. Since common numerical solution techniques such as the shooting method are local in nature and hence are difficult to use to find multiple solutions, an alternative formulation of the problem is presented that can be solved through homotopy methods for polynomial systems. These methods are guaranteed to find all solutions within the resolution of the system description's discretization. Specifically, this paper studies a group of unicycle-like autonomous mobile robots operating in a 2-dimensional obstacle-free environment. Each robot has a predefined initial state and final state and the problem is to find the optimal path between two states for every robot. The path is optimized with respect to the control effort and the deviation from a desired formation. The bifurcation parameter is the relative weight given to penalizing the deviation from the desired formation versus control effort. It is shown that as this number varies, bifurcations of solutions are obtained. Considering the common use of optimization methods in robotic navigation and coordination problems, understanding the existence and structure of bifurcating and multiple solutions is of great importance in robotics.