Author name cluster

Robin Ritz

Possible papers associated with this exact author name in Arrow. This page groups case-insensitive exact name matches and is not a full identity disambiguation profile.

7 papers

1 author row

ICRA Conference 2017 Conference Paper

A global controller for flying wing tailsitter vehicles

Robin Ritz
Raffaello D'Andrea

We present a global controller for tracking nominal trajectories with a flying wing tailsitter vehicle. The control strategy is based on a first-principles model of the vehicle dynamics that captures all relevant aerodynamic effects, and we apply an onboard parameter learning scheme in order to estimate unknown aerodynamic parameters. A cascaded control architecture is used: Based on position and velocity errors an outer control loop computes a desired attitude keeping the vehicle in coordinated flight, while an inner control loop tracks the desired attitude using a lookup table with precomputed optimal attitude trajectories. The proposed algorithms can be implemented on a typical microcontroller and the performance is demonstrated in various experiments.

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IROS Conference 2015 Conference Paper

Design and implementation of an unmanned tail-sitter

Roman Bapst
Robin Ritz
Lorenz Meier
Marc Pollefeys

We present the design and implementation of a small Vertical-Take-Off-and-Landing (VTOL) aircraft. The vehicle requires minimal additional components to achieve the hover capability and is thus very efficient in forward flight. We improve over the state of the art by using a single controller in all flight modes without using blending between hover condition and fixed wing controllers or gain scheduling. We present a compact airflow estimation model for VTOL airframes which rely on the slipstream across control surfaces for hover attitude control. Furthermore we show attitude and position control results in simulation. Finally we show outdoor flight experiments validating our simulation results.

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IROS Conference 2015 Conference Paper

High-speed, steady flight with a quadrocopter in a confined environment using a tether

Maximilian Schulz
Federico Augugliaro
Robin Ritz
Raffaello D'Andrea

This paper presents a method that enables highspeed, steady flight in confined spaces for tethered quadrocopters. Thanks to the centripetal force exerted by the tether, high-speed trajectories along circles at different velocities, accelerations, and orientations in space can be flown. Various circular maneuvers are experimentally demonstrated, and tangential velocities of up to 15 m/s and centripetal accelerations of more than 13 g can be achieved in steady flight. The recorded data allows to characterize the flight behavior of quadrocopters at high airspeeds: As an example, an estimate of the actual thrust produced by the motors and of the aerodynamic drag acting on the vehicle is presented. An accompanying video shows tethered quadrocopters performing high-speed maneuvers.

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ICRA Conference 2014 Conference Paper

An on-board learning scheme for open-loop quadrocopter maneuvers using inertial sensors and control inputs from an external pilot

Robin Ritz
Raffaello D'Andrea

We present an iterative learning scheme for improving the performance of highly dynamic open-loop maneuvers with quadrocopters. A probabilistic estimate of the state deviation at the end of the maneuver is obtained by fusing two data sources that are available on-board: 1) an inertial measurement unit, and 2) control inputs from an external pilot that performs a recovery after the open-loop maneuver has been executed. A computationally lightweight policy gradient method is applied in order to adapt a set of characteristic maneuver parameters, which in turn reduces the expected value of the final state deviation for the next execution of the maneuver. The performance of the learning algorithm is demonstrated in the ETH Zurich Flying Machine Arena by improving the performance of a triple flip.

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IROS Conference 2013 Conference Paper

Carrying a flexible payload with multiple flying vehicles

Robin Ritz
Raffaello D'Andrea

This paper introduces a method for carrying a flexible payload with multiple attached flying vehicles. A model for a particular class of flexible structures is presented, and an estimator is derived that observes the pose of the structure in space as well as the magnitude of some characteristic deformation modes. A control strategy that controls the flexible payload to a desired pose while also controlling the deformations to zero is introduced. The presented methods are validated in the ETH Zurich Flying Machine Arena by flying with a thin, flexible ring that is carried by six quadrocopters.

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IROS Conference 2012 Conference Paper

Cooperative quadrocopter ball throwing and catching

Robin Ritz
Mark W. Mueller
Markus Hehn
Raffaello D'Andrea

This paper presents a method for enabling a fleet of circularly arranged quadrocopters to throw and catch balls with a net. Based on a first-principles model of the net forces, nominal inputs for all involved vehicles are derived for arbitrary target trajectories of the net. Two algorithms that generate open-loop trajectories for throwing and catching a ball are also introduced. A set of throws and catches is demonstrated in the ETH Zurich Flying Machine Arena testbed.

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IROS Conference 2011 Conference Paper

Quadrocopter performance benchmarking using optimal control

Robin Ritz
Markus Hehn
Sergei Lupashin
Raffaello D'Andrea

A numerical method for computing quadrocopter maneuvers between two states is presented. Computed maneuvers satisfy Pontryagin's minimum principle with respect to time-optimality. First, in order to obtain the structure of time-optimal maneuvers, we apply the minimum principle to a first-principles, two-dimensional quadrotor model. Then we present a numerical algorithm that enables the computation of maneuvers for arbitrary initial and final states. The developed method is used to compute a set of maneuvers, which are discussed and demonstrated experimentally in the ETH Zurich Flying Machine Arena testbed.

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