Michael Heidingsfeld

Reversing the General One-Trailer System: Asymptotic Curvature Stabilization and Path Tracking

Backing up a trailer can be a challenge, particularly for inexperienced recreational drivers. We therefore develop two feedback controllers, which support the driver with automatic steering inputs in various situations. Based on the kinematics of the general one-trailer system, we first derive an input/output-linearizing control law that asymptotically stabilizes a given curvature for the trailer. This enables the driver to directly steer the trailer, e.g., by means of a turning knob, such that the trailer will automatically be prevented from jackknifing. The control task is then modified and solved so that the vehicle can also take over the complete stabilization task along given paths. In combination with a path-planning algorithm, this enables automated parallel parking for example. The complete system is implemented on a rapid-prototyping environment and evaluated in real-world scenarios.

Development of an arm support system to improve ergonomics in laparoscopic surgery: study design and provisional results.

BackgroundLaparoscopic surgery (LS) induces physical stress to the surgeon that is associated with an increased prevalence of musculoskeletal pain and injury in the shoulder–neck region. The aim of this research project is to develop an arm support system (ASsyst) that reduces physical stress and is applicable to various laparoscopic interventions and operation room settings.MethodsA systematic approach to develop an ASsyst started in October 2012 consisting of five consecutive steps. In step 1, 14 laparoscopic interventions were observed using subjective and objective measures to determine key indicators for the conception of an ASsyst in LS. In step 2, an expert workshop was held to find and evaluate solutions to generate concepts for a support system based on the results of step 1 and general methods. During the third step, prototypes of ASsyst were tested in an experimental setting. Steps 4 and 5 are currently in process and include the final development of the ASsyst using the most promising concept for the evaluation during simulated LS.ResultsIncreased levels of physical stress were found in LS. Asymmetric strains were common. Three prototypes of ASsyst emerged from step 1 and 2. These prototypes were a cable construction with a noose for the lower arm, a support from below the elbow and a pneumatic vest supporting the upper arm. The experimental testing of these prototypes demonstrated reduced physical stress when compared to the unsupported environment. The support from below the elbow seemed to be the most practical in terms of implementation in various operation room settings and acceptance by surgeons. Step 4 and 5 are still in process.ConclusionsErgonomic problems have been identified in LS that could be addressed by an ASsyst. The concept of supporting the elbow from below has been found to be the most promising approach.

A force-controlled human-assistive robot for laparoscopic surgery

In this contribution a novel human-assistive robot for laparoscopic surgery is presented. The purpose of the proposed system is to improve the ergonomics of laparoscopic surgery by reducing the physical load on the surgeon. Selected examples of existing robotic systems for medical and manufacturing applications are compared to the suggested system. After a brief description of the systems main features, a velocity-based admittance controller for regulating the interaction force is introduced. The desired interaction force is the sum of the required supporting force and a force-feedback, signalizing workspace constraints. The supporting force varies in magnitude and direction depending on the surgeons posture and allows for individual adjustments to the needs of the surgeon on duty.

Model-based sensor fault diagnosis for the Stuttgart SmartShell

The present paper proposes a concept for model-based sensor fault diagnosis and its application to the reference system Stuttgart SmartShell. The approach is based on the well-known Dedicated Observer Scheme and utilizes observable subsystems for residual generation. Particular attention is paid to the residual evaluation in order to account for the effects of noise, model uncertainties and external disturbances. The approach is evaluated in simulation and experiment. The results indicate, that the proposed concept is well suited for the isolation of additive sensor faults despite the presence of moderate disturbances.

Gramian-based actuator placement with spillover reduction for active damping of adaptive structures

Adaptive structures are engineering structures with the ability to modify their response to external loads. This includes active damping of externally induced vibrations. The controller design is usually based on reduced order models that comprise the most important vibration modes of the structure. This can lead to unwanted excitation of the neglected modes, known as control spillover. One means to cope with this problem is by proper placement of the actuators. In this contribution, we present a method for optimal actuator placement for active damping of adaptive structures that explicitly considers spillover effects by optimizing the trade-off between controllability of the considered and neglected modes. The optimization criterion is based on the controllability Gramian. Under certain conditions, the globally optimal solution can be found. The proposed method is applied to a numerical example of a high-rise truss structure.

Multimodal sensor fusion of inertial, strain, and distance data for state estimation of adaptive structures using particle filtering

This contribution depicts an evaluation of the potential of state estimation techniques in the context of adaptive structures. Those techniques are necessary, as the control algorithms acting on the actuators of the adaptive structures need to know the systems state, but not all states are accessible for measurement. We model and simulate a truss structure, which is equipped with inertial sensors, strain gauges, and an optical scanning system. The latter performs a point-wise scan of the truss structures surface, which renders the measurement equation time-varying. The truss structure is excited by wind in the simulation. We implement a particle filter in order to perform the multimodal sensor fusion and state estimation. The particle filter shows good results for both an unexcited scenario as well as for a wind excitation scenario. We discuss the results as well as the implications for the active control of adaptive structures.

On steady-state disturbance compensability for actuator placement in adaptive structures

Abstract Adaptive structures in civil engineering are mechanical structures with the ability to modify their response to external loads. Actuators strongly affect a structure’s adaptivity and have to be placed thoughtfully in the design process to effectively compensate external loads. For constant loads, this property is introduced as steady-state disturbance compensability. This property can be linked to concepts from structural engineering such as redundancy or statical indeterminacy, thus representing an interdisciplinary approach. Based on the disturbance compensability matrix, a scalar performance metric is derived as quantitative measure of a structure’s ability to compensate the output error for arbitrary constant disturbances with a given set of actuators. By minimizing this metric, an actuator configuration is determined. The concept is applied to an example of a truss structure.

Potential of origami-based shell elements as next-generation envelope components

Building envelopes manage several crucial functions, including structural, thermal, hygric and aesthetic functions. Classic façade concepts usually work with static elements like glass, metal or composite panels that primarily provide protection against the elements, and an additional layer of active systems that manage dynamic tasks like light protection or thermal regulation. Kinematic shell elements offer new ways to incorporate multiple dynamic functionalities into cladding elements, and thus can help to generate new active, efficient and aesthetic envelopes. We will introduce the concept of origami-inspired multifunctional shell elements and discuss potential applications.

Introduction, mathematical modelling and motion control of the novel pneumatic textile actuator

Abstract This paper introduces a novel type of pneumatic actuator, namely the pneumatic textile actuator (PTA). Although the operating principle is similar to pneumatic artificial muscles, design, fabrication and properties of PTAs show significant differences. PTAs consist of double-layered textiles, fabricated in one piece using the Jacquard weaving technology. By filling the chamber between the two layers with pressurised air, one obtains a low-weight, high-power pneumatic actuator at very low cost. The paper first describes the design, fabrication and properties of PTAs in general. Then, the characteristics of a specific PTA are determined experimentally. Moreover, we derive a mathematical model of the dynamic behaviour of the PTA. The model forms the basis for a motion control algorithm, combining flatness-based feedforward and linear feedback control. Finally, the performance of the controller is evaluated experimentally. The results indicate that PTAs are well suited for motion control tasks requiring small displacements but high forces and minimum actuator weight.

Analysis of body‐, arm‐ and hand‐posture and the human‐machine‐interaction when using an arm‐support‐device for laproscopic surgery – results of an evaluation in laboratory setting

The aim of this article is the analysis of a multidisciplinary developed first prototype of an innovative Arm‐Support‐Device (ASD) for laparoscopic surgery. This device follows the motions of the leaned lower arm of the surgeon and supports the posture in order to relief the surgeon. During the multidisciplinary development process, important requirements of surgeons from gynecology and urology were compiled. Requirements like physical relief and usability‐enhancement when using comparable techniques are shown in some studies. The fulfillment of further important requirements concerning the human‐machine‐interaction between surgeon and ASD as well as the effects of the ASD on the body‐, arm‐ and hand‐posture of the surgeon are analyzed in this study. Therefore 12 surgeons performed simulated laparoscopic static and dynamic tasks on a so‐called pelvi‐trainer in laboratory‐setting using the developed ASD and without using the ASD. For analysis life‐record data from two perspectives (frontal and sagittal), the method of thinking aloud and the interview were used. The analysis shows that body‐, arm‐ and hand postures of the surgeons are mainly similar independent of the use of the ASD. The surgeons used the ASD intuitively for getting in, operating and getting out, which were important requirements. Nevertheless a familiarization is necessary. It is expected that some deficits of the ASD‐prototype can be avoided in the possible next step of developing an end‐design‐product by using the results of this study. These deficits are skidding down of the arm of the surgeon from the support for some steeper arm‐postures and rarely appearing collision of the support with the fixed endoscope.