Papers by Konstantin Kondak
2018 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)
This paper presents a passive compliance control for aerial manipulators to achieve stable enviro... more This paper presents a passive compliance control for aerial manipulators to achieve stable environmental interactions. The main challenge is the absence of actuation along body-planar directions of the aerial vehicle which might be required during the interaction to preserve passivity. The controller proposed in this paper guarantees passivity of the manipulator through a proper choice of end-effector coordinates, and that of vehicle fuselage is guaranteed by exploiting time domain passivity technique. Simulation studies validate the proposed approach.
Journal of Intelligent & Robotic Systems, 2021
This paper introduces a passivity-based control framework for multi-task time-delayed bilateral t... more This paper introduces a passivity-based control framework for multi-task time-delayed bilateral teleoperation and shared control of kinematically-redundant robots. The proposed method can be seen as extension of state-of-the art hierarchical whole-body control as it allows for some of the tasks to be commanded by a remotely-located human operator through a haptic device while the others are autonomously performed. The operator is able to switch among tasks at any time without compromising the stability of the system. To enforce the passivity of the communication channel as well as to dissipate the energy generated by the null-space projectors used to enforce the hierarchy among the tasks, the Time-Domain Passivity Approach (TDPA) is applied. The efficacy of the approach is demonstrated through its application to the DLR Suspended Aerial Manipulator (SAM) in a real telemanipulation scenario with variable time delay, jitter, and package loss.
2019 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), 2019
Complex aircraft systems are becoming a target for automation. For successful operation, they req... more Complex aircraft systems are becoming a target for automation. For successful operation, they require both efficient and readable mission execution system (MES). Flight control computer (FCC) units, as well as all important subsystems, are often duplicated. Discrete nature of MES does not allow small differences in data flow among redundant FCCs which are acceptable for continuous control algorithms. Therefore, mission state consistency has to be specifically maintained. We present a novel MES which includes FCC state synchronization. To achieve this result we developed the new concept of Asynchronous Behavior Tree with Memory (ABTM) and proposed a state synchronization algorithm. The implemented system was tested and proven to work in a real-time simulation of High Altitude Pseudo Satellite (HAPS) mission.
2019 19th International Conference on Advanced Robotics (ICAR), 2019
Despite being able to ensure passivity of teleoperation systems, Time Domain Passivity Approach (... more Despite being able to ensure passivity of teleoperation systems, Time Domain Passivity Approach (TDPA), causes an undesired effect, namely position drift. Although previous works focused on developing TDPA-based drift compensation methods to solve this issue, no multi-DoF treatment has been addressed. In that scope, this paper focuses on providing an extension of previous TDPA-based approaches to multi-DoF Cartesian-space teleoperation by exploring the Euclidean group of rigid body motions and the exponential map that relates it to its Lie algebra. The applicability of the proposed method to multi-DoF devices is validated through numerical simulation with round-trip time delays of 700 ms.
2020 IEEE International Conference on Robotics and Automation (ICRA), 2020
This paper presents a design of oscillation damping control for the cable-Suspended Aerial Manipu... more This paper presents a design of oscillation damping control for the cable-Suspended Aerial Manipulator (SAM). The SAM is modeled as a double pendulum, and it can generate a body wrench as a control action. The main challenge is the fact that there is only one onboard IMU sensor which does not provide full information on the system state. To overcome this difficulty, we design a controller motivated by a simplified SAM model. The proposed controller is very simple yet robust to model uncertainties. Moreover, we propose a gain tuning rule by formulating the proposed controller in the form of output feedback linear quadratic regulation problem. Consequently, it is possible to quickly dampen oscillations with minimal energy consumption. The proposed approach is validated through simulations and experiments.
Compliant robot control for dexterous mobilemanipulation: on ground, in space and on air
2020 IEEE International Conference on Robotics and Automation (ICRA), 2020
Attaching a robotic manipulator to a flying base allows for significant improvements in the reach... more Attaching a robotic manipulator to a flying base allows for significant improvements in the reachability and versatility of manipulation tasks. In order to explore such systems while taking advantage of human capabilities in terms of perception and cognition, bilateral teleoperation arises as a reasonable solution. However, since most telemanipulation tasks require visual feedback in addition to the haptic one, real-time (task-dependent) positioning of a video camera, which is usually attached to the flying base, becomes an additional objective to be fulfilled. Since the flying base is part of the kinematic structure of the robot, if proper care is not taken, moving the video camera could undesirably disturb the end-effector motion. For that reason, the necessity of controlling the base position in the null space of the manipulation task arises. In order to provide the operator with meaningful information about the limits of the allowed motions in the null space, this paper presents...
2019 International Conference on Robotics and Automation (ICRA), 2019
High risk of a collision between rotor blades and the obstacles in a complex environment imposes ... more High risk of a collision between rotor blades and the obstacles in a complex environment imposes restrictions on the aerial manipulators. To solve this issue, a novel system cable-Suspended Aerial Manipulator (SAM) is presented in this paper. Instead of attaching a robotic manipulator directly to an aerial carrier, it is mounted on an active platform which is suspended on the carrier by means of a cable. As a result, higher safety can be achieved because the aerial carrier can keep a distance from the obstacles. For self-stabilization, the SAM is equipped with two actuation systems: winches and propulsion units. This paper presents an overview of the SAM including the concept behind, hardware realization, control strategy, and the first experimental results.
2021 International Conference on Unmanned Aircraft Systems (ICUAS), 2021
Providing the operator with a good view of the remote site is of paramount importance in aerial t... more Providing the operator with a good view of the remote site is of paramount importance in aerial telemanipulation. In light of that, this paper proposes the application of a hierarchical control framework in order to tackle the problem of adjusting the field of view of an on-board camera as a secondary task. The proposed approach ensures that the flying base, and consequently the camera, can be steered in order to provide a distant operator with a desired field of view without disturbing the end-effector pose. The approach is focused on aerial manipulators with torque-controlled arms, like the DLR Suspended Aerial Manipulator (SAM), while allowing the base to be directly torque-controlled or, alternatively, through an inner-loop velocity controller. Quantitative, qualitative, and real-scenario experimental validation is carried out using the SAM and confirms the need for such an approach and its efficacy in achieving decoupled field-of-view control.
2016 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), 2016
This paper is devoted to the performance optimization of an aerial manipulation system composed o... more This paper is devoted to the performance optimization of an aerial manipulation system composed of a Flettner-helicopter and 7 DoF manipulator. With experiments we demonstrate that the time delays in signal propagation between perception and actuation modules play an important role for the overall performance of an aerial manipulator system using visual servoing. We present an approach for estimation of the perception-action time delay and its active compensation based on the predicted motion of the manipulator end-effector. Experiments show that compensating these delays improve the manipulation performance even more than elaborated methods for cooperative arm-helicopter control. The proposed approach should not be considered as a replacement of armhelicopter coordinated control but as an extension. Additionally the reliability of the visual servoing is improved by implementing a multi object localization that is robust to occlusions of the target object. The accuracy and robustness of the proposed visual servoing and active compensation algorithms are demonstrated in inand outdoor experiments With the proposed algorithm the aerial manipulator is able to repeatedly grasp an object with an accuracy better than 2cm.
2021 International Conference on Unmanned Aircraft Systems (ICUAS), 2021
High Altitude Long Endurance (HALE) aircraft can take flight to altitudes as high as 20 km and ca... more High Altitude Long Endurance (HALE) aircraft can take flight to altitudes as high as 20 km and can stay there for long periods of time. In this article, the viability of landing such an aircraft on a mobile platform using a cooperative control strategy for motion synchronization is examined. Time domain system identification is applied to create a model of the Elektra 2 Solar HALE aircraft, which was found to be high fidelity by the Federal Aviation Administration (FAA) standards. An analysis is made to evaluate the feasibility of autonomously landing the HALE Unmanned Aerial Vehicle (UAV) on top of a ground vehicle with a roof-mounted landing platform. Controller synthesis is done for the individual vehicles as well as the cooperative landing control, leading to an examination of the overall system stability and performance, using both deterministic and stochastic methods.
IEEE Robotics and Automation Letters, 2020
Energy-based cooperative control for landing fixed-wing uavs on mobile platforms under communicat... more Energy-based cooperative control for landing fixed-wing uavs on mobile platforms under communication delays.
Proceedings of the 10th Aerospace Technology Congress, October 8-9, 2019, Stockholm, Sweden, Oct 23, 2019
Developed by Elektra Solar, an official spin-off of the DLR Institute for Robotics and Mechatroni... more Developed by Elektra Solar, an official spin-off of the DLR Institute for Robotics and Mechatronics (DLR-RMC), the Elektra 2 is a solar-powered autonomous aircraft designed to endure long distances as well as high altitudes. The main motivation of this work is to develop a sensor fault detection and reconfiguration (FDR) approach to be applied to the Elektra 2 Aircraft. Currently, the Elektra 2 Solar aircraft provides a simple limit-checking of certain IMU measurements such as aircraft angular velocities and pitch, roll and yaw angles. In the proposed FDR approach, residual generation for both longitudinal and lateral dynamics of the aircraft is achieved based on the design of Kalman filters. Combined with the sequential probability ratio test (SPRT) as a decision function, selected aircraft sensor residuals are evaluated using an adaptive threshold with low sensitivity to control signal variation and noise and high sensitivity to fault symptoms. Due to the critical aspects of IMU faults, the reconfiguration action is defined as switching from primary IMU to backup IMU in case of fault occurrence.
IFAC-PapersOnLine, 2018
This paper presents an approach to damp out the oscillatory motion of the pendulum-like hanging p... more This paper presents an approach to damp out the oscillatory motion of the pendulum-like hanging platform on which a robotic manipulator is mounted. To this end, moving masses were installed on top of the platform. In this paper, asymptotic stability of the platform (which implies oscillation damping) is achieved by designing reference acceleration of the moving masses properly. A main feature of this work is that we can achieve asymptotic stability of not only the platform, but also the moving masses, which may be challenging due to the under-actuation nature. The proposed scheme is validated by the simulation studies.
IEEE Robotics and Automation Letters, 2018
Stability is not trivial in aerial manipulation tasks because of the dynamical coupling between t... more Stability is not trivial in aerial manipulation tasks because of the dynamical coupling between the aerial vehicle and the manipulator. This is especially true when the manipulator becomes heavy, so that its dynamics can be significant. In this letter, a stabilizing controller for the regulation of overall system will be designed without using any assumptions on the dynamic model. In addition, thorough discussion with simulation validation is presented. Index Terms-Aerial systems: mechanics and control, motion control. I. INTRODUCTION I N RECENT years, as a natural extension of successful achievements in unmanned aerial vehicle (UAV) studies, aerial manipulation has become an emerging research field. In this field, there are many interesting research branches such as mechanical design [1]-[4], modeling methodology [5], [6], and intelligence [7]-[9]. In addition to these, control design is also an important branch to accomplish successful aerial manipulation. Control of UAV-manipulator (in short, UAV-M hereinafter) system is a quite complicated problem because the UAV is dynamically coupled with the robotic manipulator, and moreover, the UAV is typically under-actuated. 1 Control problem becomes especially important when the dynamics of the manipulator becomes significant. One example is the UAV-M in Fig. 1(a) which is equipped with a 7 Degrees of Freedom (DoF) manipulator. Since the manipulator weighs about 14 kg (while the UAV body weighs around 35 kg), the dynamics of the manipulator can significantly affect that of the UAV, and vice versa. Our previous study [11] has shown that, while the UAV is hovering, manipulator's simple swing motion can actually cause instability. To overcome this, [12] showed that UAV and manipulator can be controlled independently if the Center of Mass (CoM) of the whole system lies on the gravity vector of the UAV. For example, [8], [13] used this strategy in the aerial manipulation tasks. However, the analysis was rather conceptual because it was based on a simplified model, and formal stability proof was not provided. Although several approaches have employed full dynamics of the UAV-M systems in control design [5], [14]-[20], formal
Journal of Systems Architecture, 2017
To address the heterogeneity and scalability issues of simulating Cooperating Objects (COs) syste... more To address the heterogeneity and scalability issues of simulating Cooperating Objects (COs) systems, we propose KASSANDRA, a conceptual framework for enabling distributed COs simulation by integrating existing simulation tools. Moreover, KASSANDRA exploits the communication middleware used by real-world COs as underlying communication mechanism for integrating KASSANDRA-enabled simulation tools. In this way, real-world COs can be included with simulated objects in a seamless way to perform more accurate system performance evaluation. Moreover, such a hardware-in-the-loop approach is not limited to pre-deployment performance analysis, and can offer possibilities to analyse performance at different phases of CO applications. The concept of KASSANDRA has been carried out in the EU PLANET project. In this paper, we introduce the KASSANDRA framework components While working on the paper, Marc Schwarzbach was associated with the German Aerospace Center (DLR),
Multi-Sensor Data Fusion for a Tethered Unmanned Helicopter Using a Square-Root Unscented Kalman Filter
Unmanned Systems, 2016
The use of tethered Unmanned Aircraft Systems (UAS) in aerial robotic applications is a relativel... more The use of tethered Unmanned Aircraft Systems (UAS) in aerial robotic applications is a relatively unexplored research field. This work addresses the attitude and position estimation of a small-size unmanned helicopter tethered to a moving platform using a multi-sensor data fusion algorithm based on a numerically efficient sigma-point Kalman filter implementation. For that purpose, the state prediction is performed using a kinematic process model driven by measurements of the inertial sensors (accelerometer and gyroscope) onboard the helicopter and the subsequent correction is done using information from additional sensors like magnetometer, barometric altimeter, LIDAR altimeter and magnetic encoders measuring the tether orientation relative to the helicopter. Assuming the tether is kept taut by an actuated device on the platform during the system operation, the helicopter position is estimated relative to the anchor point. Although this configuration avoids the need of a GPS, a sta...
Robotics and Autonomous Systems, 2016
First experimental results on enhancing hovering performance of unmanned helicopters by using a t... more First experimental results on enhancing hovering performance of unmanned helicopters by using a tethered setup, Robotics and Autonomous Systems (2016),
IEEE Robotics and Automation Letters, 2016
This paper addresses the problem of landing a VTOL UAV using a serial robotic manipulator fixed t... more This paper addresses the problem of landing a VTOL UAV using a serial robotic manipulator fixed to the landing surface, which assists the UAV during the last, most challenging, landing phase. In this phase, UAV and manipulator are connected via a universal hinge, which decouples the flying vehicle's and the robot's end-effector orientation. This novel system is meant to be used for VTOL UAVs landing on moving platforms under severe environmental conditions. The main contribution of the paper is the design of a linear state-space controller for position and orientation of the UAV while it is fixed to the manipulator. Furthermore, we compare a coupled and a decoupling realization of the model-based controller with a model-free controller. Both model-based controllers consider the dynamics of an attitude-controlled aerial vehicle and use the acceleration of the robot's end-effector as control input. The decoupling controller allows to fully actuate the UAV using the manipulator in addition to the UAV's actuators. All three controllers are validated and compared in experiments using a KUKA/DLR lightweight robot on a non-moving base and an AR.Drone 2.0 quadrotor. The experimental results show that decoupling is superior to the coupled and the model-free approach, since the orientation of the UAV rotorcraft is controlled more precisely.
This paper is devoted to lightweight rotary wing UAVs for applications at extreme high altitudes ... more This paper is devoted to lightweight rotary wing UAVs for applications at extreme high altitudes of up to 9000m, such as search and rescue as well as different types of environmental monitoring. Up to now, such rotary wing UAVs have not been available. Consequently, experience in design and operation of rotary wing UAVs in such environments is lacking. This situation motivates our team from DLR and TUM to work on an all-electric prototype of this kind of rotary wing UAV. The first experimental missions should be performed at altitudes of 5000 to 9000m above sea level. This paper shows the project’s current status and preliminary results. We present procedures for preliminary rotor designs and electrical power supplies as well as a tool developed for exploration of the influence of critical design parameters from a mission based point of view. Using the described procedures and the tool, we present the preliminary design of the UAV prototype, which is a synchropter with two counter-r...
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Papers by Konstantin Kondak