Klaus Janschek

Space Application of a Self-Calibrating Optical Processor for Harsh Mechanical Environment

Abstract An optical image processing device based on a Joint Transform Optical Correlator provides high processing speed and could be very usable in real-time image processing applications. In harsh mechanical environment the performance of the correlator could degrade due to mechanical deformations of the optical system. With special self-calibration methods the Joint Transform Optical Correlator can be built insensitive to mechanical disturbances.

Optical Correlator for Image Motion Compensation in the Focal Plane of a Satellite Camera

Abstract The paper presents the concept of a system for the compensation of the image motion in the focal plane of a satellite camera. The image motion is compensated by corresponding shift of the image sensor, controlled through direct visual feedback. The system includes an auxiliary image sensor and an optical correlator for the high precision measurement of the motion of a dark and fast moving focal plane image. Questions of system realisation are considered, expected performances are estimated on base of the optical correlator hardware model testing

Integrated camera motion compensation by real-time image motion tracking and image deconvolution

This paper presents the concept of a smart satellite pushbroom imaging system with internal compensation of attitude instability effects. The compensation is performed within the optical path by an active opto-mechatronic stabilization of the focal plane image motion in a closed loop system with visual feedback. Residual distortions are corrected by image deblurring through deconvolution. Both corrective actions are derived from a real-time image motion measurement which is based on an auxiliary matrix image sensor and an onboard optical correlator. The paper describes the principles of operation, the main system elements and gives detailed performance figures derived from a simulation performance model, which contains all relevant components of the smart imaging system

Airborne test results for smart pushbroom imaging system with optoelectronic image correction

Smart pushbroom imaging system (SMARTSCAN) solves the problem of image correction for satellite pushbroom cameras which are disturbed by satellite attitude instability effects. Satellite cameras with linear sensors are particularly sensitive to attitude errors, which cause considerable image distortions. A novel solution of distortions correction is presented, which is based on the real-time recording of the image motion in the focal plane of the satellite camera. This allows using such smart pushbroom cameras (multi-/hyperspectral) even on moderately stabilised satellites, e.g. small sats, LEO comsats. The SMARTSCAN concept uses in-situ measurements of the image motion with additional CCD-sensors in the focal plane and real-time image processing of these measurements by an onboard Joint Transform Optical Correlator. SMARTSCAN has been successfully demonstrated with breadboard models for the Optical Correlator and a Smart Pushbroom Camera at laboratory level (satellite motion simulator on base of a 5 DOF industrial robot) and by an airborne flight demonstration in July 2002. The paper describes briefly the principle of operation of the system and gives a description of the hardware model are provided. Detailed results of the airborne tests and performance analysis are given as well as detailed tests description.

An Embedded Optical Flow Processor for Visual Navigation using Optical Correlator Technology

The conceptual design of an embedded high performance opto-electronic optical flow processor is presented, which is designed for navigation applications in the field of robotics (ground, aerial, marine) and space (satellites, landing vehicles). It is based on 2D fragment image motion determination by 2D correlation. To meet the real-time performance requirements the principle of joint transform correlation (JTC) and advanced optical correlator technology is used. The paper recalls briefly the underlying principles of optical flow computation and optical correlation, it shows the system layout and the conceptual design for the optical flow processor and it gives preliminary performance results based on a high fidelity simulation of the complete optical processing chain

Optical-correlator-based system for the real-time analysis of image motion in the focal plane of an Earth observation camera

The paper describes the design concept of an optoelectronic system for real time image motion analysis. The system is proposed to be used onboard an Earth observation satellite for the real time recording of the image motion in the focal plane of the camera. With this record available, it is possible to use pushbroom scan cameras onboard satellites with moderate attitude stability (possible geometric distortions, caused by the attitude instability, can be corrected posteirori on base of the records). New experimental results are presented, which have been derived from a real-time breadboard model of the optical processor, developed and manufactured under ESA- contract. The results of the tests are provided as well as the expected performances of a full scale system.

Compensation of focal plane image motion perturbations with optical correlator in feedback loop

The paper presents a concept of a smart pushbroom imaging system with compensation of attitude instability effects. The compensation is performed by active opto-mechatronic stabilization of the focal plane image motion in a closed loop system with visual feedback on base of an auxiliary matrix image sensor and an onboard optical correlator. In this way the effects of the attitude instability, vibrations and micro shocks can be neutralized, the image quality improved and the requirements to satellite attitude stability reduced. To prove the feasibility and to estimate the effectiveness of the image motion stabilization, a performance model of the smart imaging system has been developed and a simulation experiment has been carried out. The description of the performance model and the results of the simulation experiment are also given.

Dual Graph Error Propagation Model for Mechatronic System Analysis

Abstract Error propagation analysis is an important part of a system development process. This paper addresses a model based analysis of spreading of data errors through mechatronic systems. Error propagation models for such kind of systems must use an abstraction level, which allows the proper mapping of the mutual interaction of heterogeneous system elements such as software, hardware and physical parts. A number of appropriate approaches have been introduced in recent years. The majority of them are based only on a data flow analysis. It is shown in this paper that for a complete picture the system control flow has to be considered as well. A new approach based on probabilistic control flow and data flow graphs is presented. The structures of the graphs can be derived systematically from an UML/SysML model of a system. The knowledge about an operational system profile allows the definition of additional system properties. Initially this model was developed for software errors localization. This paper shows its applicability to the error propagation analysis of an entire mechatronic system. The paper presents the modeling concept, the complete mapping process and application of the model for error localization. A reference robot control example demonstrates the main modeling steps.

Nonsmooth Predictive Control for Wiener Systems With Backlash-Like Hysteresis

In this paper, a nonsmooth predictive control method for Wiener systems with backlash-like hysteresis is proposed. In this type of system, the backlash-like hysteresis is connected in series with a preceded linear dynamic subsystem. A backlash-like hysteresis is modeled as a nonsmooth function with multivalued mapping; the corresponding objective function of the control system is also defined as being nonsmooth. In this case, the implementation of conventional model predictive control for such systems will encounter a challenge, since the gradients of the control criterion function with respect to control variables do not exist at nonsmooth points. In order to solve this problem, a nonsmooth receding horizon strategy based on Clarke subgradients is proposed. Moreover, the robust stability of the predictive control of such nonsmooth Wiener systems is analyzed. Finally, a numerical example and a simulation study on a mechanical transmission system are implemented to validate the proposed method.

SmartScan -- hardware test results for smart opto-electronic image correction for pushbroom cameras

The paper describes the test results of the hardware model of a smart pushbroom imaging system. The imaging system can be used on satellites with moderately attitude stability due to application of the image correction on base of the real-time image motion record by an optoelectronic image processor and auxiliary sensors in the focal plane. The tested model includes the breadboard model of a smart pushbroom camera with auxiliary sensors, the optoelectronic processor model and the image correction software. The tests have been performed on a laboratory satellite motion simulator based on a 5 DOF industrial robot. Numerical values of the image motion record accuracy and the image correction efficiency are given as well as a detailed test description.