Search

This paper presents a new vision tracking system for mobile robot by integrating information received from encoders, inertial sensors, and active beacons. The proposed system accurately determines mobile robot position and orientation using relative and absolute position estimates, and rotates the camera towards the target during locomotion. Among the implemented sensors, the encoder data give relatively accurate robot motion information except when wheels slip. On the other hand inertial sensors have the problem of integration of noisy data, while active beacons are slow when compared to other sensors. The designed system compensates the sensors limitations and slip error by switching between two Kalman filters, built for slip and no-slip cases. Each Kalman filter uses different sensors combination and estimates robot motion respectively. The slip detector is used to detect the slip condition by comparing the data from the accelerometer and encoder to select the either Kalman filter as the output of the system. Based on the proposed sensor fusion method, a vision tracking system is implemented on a two-wheeled robot. The experimental results depict that proposed system is able to locate robot position with significantly reduced position errors and successful tracking of the target for various environments and robot motion scenarios.

This paper presents a vision tracking system, based on the robot motion and vision information. For mobile robots, it is difficult to collect continuous vision information while they are in motion due to the unstable vision information. To solve this problem, the proposed vision tracking system estimates the robot position relative to a target and rotates a camera towards the target based on the estimated position information. This concept is derived from the human eye reflex mechanisms, known as the Vestibulo-Ocular Reflex (VOR) and the Opto-Kinetic Reflex (OKR). In the proposed vision tracking system, the VOR concept for compensating the head motion is realized by the feedforward control using the robot motion information from a 3-axis gyroscope and wheel encoders. To realize the OKR concept, targeting errors are periodically compensated by using the vision feedback information. An actuation module consists of pan/tilt motion motors and the camera which performs the pan and tilt functions to locate a target at the center of an image plane. The proposed vision tracking system is integrated with a two-wheeled robot. The performance of the proposed system is evaluated by extensive experiments. The proposed system shows a significant improvement in tracking performance with small targeting error. Also, the necessities of the position feedforward and vision feedback controls are verified by the experiments for the illumination change condition and the static tilting motion.

This paper addresses a stable vision system for indoor moving robot using encoder information. The proposed system uses encoder signals to calculate robot motion and rotates the camera in order to fix the target on the image frame during locomotion. Since the calculation of rotating angle of the camera is based on the integration of encoder data over time, this leads to the unbounded accumulation of error. To prevent the error accumulation, vision sensor signals are used periodically to compensate for the errors. The resulting standard deviations of the rotated camera angle error were 0.94°, 0.32° and 1.55° for rotation, translation and rotation-translation combined motion while the robot heading angles have standard deviations of 23.27°, 16.56° and 48.53°, respectively. However, the system shows performance degradation in slippery ground conditions. In our experiments the errors have trends to increase with the decrease of friction coefficient between the ground and the robot wheels. Future work should overcome this problem using additional sensors such as inertial measurement units (IMUs) that are able to detect the correct robot motion even in the case of slip disturbance.

A wafer-level vacuum packaged x and y axis gyroscope is fabricated on a (111) SOI wafer using the extended SBM (sacrificial bulk micromachining) process. The gyroscope uses vertically offset combs to resonate the proof mass in the vertical plane, and lateral combs to sense the Coriolis force in the horizontal plane. The extended SBM process is a simple two-mask process, and because all structural parts and combs are defined in one mask level, there is no misalignment in any structural parts or comb fingers. The silicon-to-glass anodic bonding carried out in low vacuum is used for the encapsulation of the fabricated gyroscope. The fabricated x and y axis gyroscope resolves 0.7 deg/sec angular rate, and the measured bandwidth is 22 Hz. The input range and the output linearity are over ± 80 deg/sec and 1.03 %FSO, respectively. The fabricated vacuum packaged x and y axis gyroscope without align error is important component at the high performance multiple-axis gyroscopes. The multiple-axis gyroscopes are used in many applications such as recently interested ubiquitous robot, car navigation, game controller, vehicle safety system, and so on.

This paper presents a LiGA (German acronym for LIthografie, Galvanoformung, Abformung) based micro biopsy actuator for the capsular endoscope. The proposed fabricated actuator aims to extract sample tissues inside small gastric intestines, that cannot be reached by conventional biopsy. The actuator size is 10 mm in diameter and 1.8 mm in length. The mechanism is of a slider-crank type. The actuator consists of trigger, rotational module, and micro biopsy tool. The core components are fabricated using the LiGA process, for overcoming the limitations in accuracy of conventional precision machining.

This paper presents a lead-lag compensator design for a MEMS-fabricated microgyroscope. The microgyroscope is basically a high Q system, thus the bandwidth is limited to be narrow. To overcome the open-loop performance limitations, a feedback controller is designed to improve the resolution, bandwidth, linearity, and bias stability of the microgyroscope. The feedback controller is applied to the z-axis microgyroscope fabricated by SBM process. In MATLAB simulations, resolution, bandwidth, input range, and bias stability of closed-loop system are improved from 0.0021 deg/sec to 0.0013 deg/sec, from 14.8 Hz to 115 Hz, from ±50 deg/sec to ±200 deg/sec, and from 0.0249 deg/sec to 0.0028 deg/sec, respectively.

This paper presents a feedback-controlled, MEMS-fabricated microgyroscope. The microgyroscope is basically a high Q system, and thus, the bandwidth is limited to be narrow. To overcome the open-loop performance limitations, a feedback controller is designed to improve the resolution, bandwidth, linearity, and bias stability of the microgyroscope. The feedback controller is applied to the z-axis microgyroscope fabricated by SBM process. The resolution, bandwidth, input range, and bias stability of closed-loop system are improved from 0.0021 deg/sec to 0.0013 deg/sec, from 14.8 Hz to 115 Hz, from ±50 deg/sec to ±200 deg/sec, and from 0.0249 deg/sec to 0.0028 deg/sec, respectively.

The difficulties in designing an effective water level controller for the nuclear steam generator arise from highly nonlinear and nonminimum-phase plant characteristics as well as nonnegative input constraint. In this paper, a modified sliding mode controller with gain scheduling is proposed for nuclear steam generator water level control. A conventional proportional-integral with feed-forward controller is also developed, and the performance of two controllers is compared in the low power range. The modified sliding mode controller shows improvements in the overshoot, undershoot, and settling time.

This paper presents a new real-time vehicle powertrain simulator. The most notable feature of the developed software is that it simulates complex vehicle powertrain dynamics, including detailed shifting transients in the PC environment in real time. The simulator can be implemented in both the DOS and WINDOWS environment. The engine sound effects are simulated using a speaker attached to a sound card. The human operated throttle input is interfaced using a sliding resistor in DOS or a pedal in WINDOWS. The processor requirements vary depending on the simulation options selected. In the basic version, this requirement is only approximately 20% of a 300 MHz Pentium II based PC. The simulator can be used for developing autonomous vehicle controllers necessary for the platoon operation in Advanced Highway Systems (AHS). For multi-vehicle platoon simulation, a network simulator is also developed in this paper. It links several simulators via the TCP/IP network. The network simulator can also be used to study the overall platoon operations and the human interface issues.