1,036 research outputs found
Interactive Co-Design of Form and Function for Legged Robots using the Adjoint Method
Our goal is to make robotics more accessible to casual users by reducing the
domain knowledge required in designing and building robots. Towards this goal,
we present an interactive computational design system that enables users to
design legged robots with desired morphologies and behaviors by specifying
higher level descriptions. The core of our method is a design optimization
technique that reasons about the structure, and motion of a robot in coupled
manner in order to achieve user-specified robot behavior, and performance. We
are inspired by the recent works that also aim to jointly optimize robot's form
and function. However, through efficient computation of necessary design
changes, our approach enables us to keep user-in-the-loop for interactive
applications. We evaluate our system in simulation by automatically improving
robot designs for multiple scenarios. Starting with initial user designs that
are physically infeasible or inadequate to perform the user-desired task, we
show optimized designs that achieve user-specifications, all while ensuring an
interactive design flow.Comment: 8 pages; added link of the accompanying vide
Running synthesis and control for monopods and bipeds with articulated
Bibliography: p. 179-20
Real-Time Motion Planning of Legged Robots: A Model Predictive Control Approach
We introduce a real-time, constrained, nonlinear Model Predictive Control for
the motion planning of legged robots. The proposed approach uses a constrained
optimal control algorithm known as SLQ. We improve the efficiency of this
algorithm by introducing a multi-processing scheme for estimating value
function in its backward pass. This pass has been often calculated as a single
process. This parallel SLQ algorithm can optimize longer time horizons without
proportional increase in its computation time. Thus, our MPC algorithm can
generate optimized trajectories for the next few phases of the motion within
only a few milliseconds. This outperforms the state of the art by at least one
order of magnitude. The performance of the approach is validated on a quadruped
robot for generating dynamic gaits such as trotting.Comment: 8 page
Natural ZMP trajectories for biped robot reference generation
The control of a biped humanoid is a challenging
task due to the hard-to-stabilize dynamics. Walking reference
trajectory generation is a key problem. Linear Inverted
Pendulum Model (LIPM) and Zero Moment Point (ZMP)
Criterion based approaches in stable walking reference
generation are reported. In these methods, generally, the ZMP
reference during a stepping motion is kept fixed in the middle of
the supporting foot sole. This kind of reference generation lacks
naturalness, in that, the ZMP in the human walk does not stay
fixed, but it moves forward under the supporting foot. This paper
proposes a reference generation algorithm based on the LIPM
and moving support foot ZMP references. The application of
Fourier series approximation simplifies the solution and it
generates a smooth ZMP reference. A simple inverse kinematics
based joint space controller is used for the tests of the developed
reference trajectory through full-dynamics 3D simulation. A 12
DOF biped robot model is used in the simulations. Simulation
studies suggest that the moving ZMP references are more energy
efficient than the ones with fixed ZMP under the supporting foot.
The results are promising for implementations
Virtual Constraints and Hybrid Zero Dynamics for Realizing Underactuated Bipedal Locomotion
Underactuation is ubiquitous in human locomotion and should be ubiquitous in
bipedal robotic locomotion as well. This chapter presents a coherent theory for
the design of feedback controllers that achieve stable walking gaits in
underactuated bipedal robots. Two fundamental tools are introduced, virtual
constraints and hybrid zero dynamics. Virtual constraints are relations on the
state variables of a mechanical model that are imposed through a time-invariant
feedback controller. One of their roles is to synchronize the robot's joints to
an internal gait phasing variable. A second role is to induce a low dimensional
system, the zero dynamics, that captures the underactuated aspects of a robot's
model, without any approximations. To enhance intuition, the relation between
physical constraints and virtual constraints is first established. From here,
the hybrid zero dynamics of an underactuated bipedal model is developed, and
its fundamental role in the design of asymptotically stable walking motions is
established. The chapter includes numerous references to robots on which the
highlighted techniques have been implemented.Comment: 17 pages, 4 figures, bookchapte
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