This paper presents a vision-based fingertip writing digits detection and recognition system using a CMOS camera and FPGA implementation. It is a real-time signature detector, since the image process algorithms are all executed in Verilog code. The experimental results show that the system can successfully recognize fingertip-numeral-writing with a accuracy rate of 95.8%.

Hybrid under-actuated control for the autonomous dynamic balance of a running electrical bicycle including frictional torque and motor dynamics is developed, where includes two control inputs: steering and pendulum voltages, and three system outputs: steering, lean and pendulum angles. Due to the under-actuated feature, two novel reference signals using three system outputs are designed so that the number of control inputs and sliding surfaces is the same. The previous fuzzy decentralized sliding mode under-actuated control (FDSMUC) is first designed. Because the uncertainties of a running electrical bicycle system, caused by different ground conditions, gusts of wind, and interactions among subsystems, are often huge, an extra compensation of learning uncertainty is plunged into FDSMUC to enhance the system performance. We call it as “fuzzy decentralized sliding mode adaptive under-actuated control (FDSMAUC).” To avoid the unnecessary transience caused by uncertainties and control signal and to preserve the balance of the bicycle, the combination of FDSMUC and FDSMAUC with a transition (i.e., Hybrid FDSMUC) is designed. Finally, the compared simulations for the suggested control system among the FDSMUC, FDSMAUC and Hybrid FDSMUC validate the efficiency of the proposed method.

This paper focuses on steering a 3D robot while walking on a flat surface. A hybrid feedback controller designed in for stable walking along a straight line is modified so that it is capable of adjusting the net yaw rotation of the robot over a step in order to steer the robot along paths with mild curvature. The controller is designed on the basis of a single pre-defined trajectory for periodic walking along a straight line. In order to illustrate the role of internal/external (i.e., medial/lateral) rotation at the hip in achieving curved walking motions, the performance of two robots, one with internal/external rotation and one without, is compared.

Based on the previous studies, the dynamic balance of an electrical bicycle includes two control inputs: steering and pendulum torques, and three system outputs: steering, lean and pendulum angles. Two novel reference signals are first designed so that the uncontrolled mode is simultaneously included into these two control modes. Two scaling factors for each subsystem are first employed to normalize the sliding surface and its derivative. The so-called fuzzy decentralized sliding-mode under-actuated control (FDSMUC) is first designed. Because the uncertainties of a bicycle system, caused by different ground conditions, gusts of wind, and interactions among subsystems, are often huge, an extra compensation of learning uncertainty is plunged into FDSMUC to enhance system performance. We call it as ldquofuzzy decentralized sliding-mode adaptive under-actuated controlrdquo (FDSMAUC). To avoid the unnecessary transient response and then destroy the balance of the bicycle, the combination of FDSMUC and FDSMAUC with a transition (i.e., fuzzy decentralized sliding-mode robust adaptive under-actuated control, FDSMRAUC) is designed. Finally, the compared simulations for an electrical bicycle among the FDSMUC, FDSMAUC and FDSMRAUC validate the efficiency of the proposed method.

This paper presents three feedback controllers that achieve an asymptotically stable, periodic, and fast walking gait for a 3-D bipedal robot consisting of a torso, revolute knees, and passive (unactuated) point feet. The walking surface is assumed to be rigid and flat; the contact between the robot and the walking surface is assumed to inhibit yaw rotation. The studied robot has 8 DOF in the single support phase and six actuators. In addition to the reduced number of actuators, the interest of studying robots with point feet is that the feedback control solution must explicitly account for the robot's natural dynamics in order to achieve balance while walking. We use an extension of the method of virtual constraints and hybrid zero dynamics (HZD), a very successful method for planar bipeds, in order to simultaneously compute a periodic orbit and an autonomous feedback controller that realizes the orbit, for a 3-D (spatial) bipedal walking robot. This method allows the computations for the controller design and the periodic orbit to be carried out on a 2-DOF subsystem of the 8-DOF robot model. The stability of the walking gait under closed-loop control is evaluated with the linearization of the restricted Poincare map of the HZD. Most periodic walking gaits for this robot are unstable when the controlled outputs are selected to be the actuated coordinates. Three strategies are explored to produce stable walking. The first strategy consists of imposing a stability condition during the search of a periodic gait by optimization. The second strategy uses an event-based controller to modify the eigenvalues of the (linearized) Poincare map. In the third approach, the effect of output selection on the zero dynamics is discussed and a pertinent choice of outputs is proposed, leading to stabilization without the use of a supplemental event-based controller.

This paper presents an improvement to ordinary voice filters that are unable to remove low frequency noise. This problem occurs because their filter parameters are over tuned, thereby destroying the speech characteristics. The proposed scheme combines NLMS, Fuzzy logic and Kalman filtering to restrain the background noise and keep the speech characteristics. This scheme is called the Normalized Fuzzy Logic Kalman Filter (NFLKF). It is especially effective when speech signals are collected in a noisy environment. Here, the output signal of the Kalman filtering is analyzed with the normalized LMS to obtain the coefficient, sigmak, and is also analyzed with the fuzzy logic to obtain the threshold, fk. Then, sigmakand fkare used together to adjust the Kalman filter parameters. This scheme can restrain the noise and improve the signal-to-noise ratio. The empirical validation is done by comparing the spectrogram from our scheme with the spectrograms from other filtering schemes, including the Normalized Least Mean Square (NLMS) Filter, the Kalman Filter and the Recursive Least Square Filter (RLS). The results show that the filtering schemes proposed can indeed restrain medium and low frequency noises which are usually difficult to handle, and does not compromise the speech characteristic. Therefore, a better signal-noise ratio is obtained and the speech quality is enhanced.

The purpose of this paper is to stabilize the running motion of an electrical bicycle. In order to do so, two strategies are employed in this paper. One is to control the bike’s center of gravity (CG), and the other is to control the angle of the bike’s steering handle. In addition, the proposed system produces three outputs that will affect the dynamic balance of an electrical bicycle: the bike’s pendulum angle, lean angle, and steering angle. Based on the data of input-output, two scaling factors are employed to normalize the sliding surface and its derivative. According to the concept of if-then rule, an appropriate rule table for the ith subsystem is obtained. Then the output scaling factor based on Lyapunov stability is determined. The proposed control method used to generate the handle torque and pendulum toque is called fuzzy sliding-mode under-actuated control (FSMUAC). The purpose of using the FSMUAC is the huge uncertainties of a bicycle system often caused by different ground conditions and gusts of wind; merely ordinary proportional-derivative-integral (PID) control method or other linear control methods usually do not show good robust performance in such situations.

In an electric bicycle, two strategies are taken up to stabilize the running motion of a bicycle. One is the control of its center of gravity (CG), and the other is the control of its steering angle of handle. In general, the control of the CG is used a pendulum. In addition, the motion of a bicycle often possesses a lean angle with respect to vertical direction. In this situation, the proposed system contains three outputs: steering angle, lean angle, and pendulum angle, these will affect the dynamic balance of an electrical bicycle. The proposed control generating the handle torque and pendulum toque is called variable structure under-actuated control (VSUAC). The motivation of using the VSUAC is that the system uncertainties of a bicycle are often huge due to different ground conditions and a gust of wind. Merely use an ordinary proportional-derivative-integral (PID) control or other linear controls often can not have good robust performance. Finally, the compared simulations for the electrical bicycle among ordinary PID control, modified proportional-derivative control (MPDC), and VSUAC confirm the usefulness of our proposed control.

Because neurosurgery and orthopedic surgery often require the drilling of bones, this paper attempts to solve the problem of bone drilling. The goal is to realize a control system, which is able to drill with a contact drilling force and can automatically stop drilling at the moment of breaking through. In particular, both the DC drilling motor control and the feed rate control are driven by force control in order to accommodate the system impedance. Moreover, the breakthrough detection is according to the threshold information of the thrust force as well as the trend of both the drilling torque and feed rate. The proposed technique has been experimentally verified through the drilling of pig bones, and the results are in accordance with the theoretical model both in the bone drilling process and at the point of breakthrough.

A machine vision system for SMT-mounting machine applications is usually a two-stage algorithm. It first measures the centroid and rotation angle of the SMD, and then checks each pin's area, position error, and grid coordinate location. In this paper, a set of complete procedures is proposed to locate and check the BGA image. During the locating procedures, we first calculate a threshold of the frame using an iterative threshold algorithm. If an object is found under this threshold, then the pin's area is calculated by the local threshold by using a momentum algorithm. After that, whether this object is a pin or not is decided by its neighbors' relative positions, the approximate rotation angle for finding the outer pins is calculated, and the centroid as well as the rotation angle of a BGA component is calculated by the rectangular least squares algorithm. The checking procedure also measures each pin's area using the momentum algorithm, then it calculates the radius of the moving sum using each pin's area, and finally measures the position error using a moving sum algorithm and judges each pin's type by gray level. The new method uses the gray level statistic information to solve the empty pad's problem and utilizes the symmetrical property of a circle to deal with the shape problem. Lastly, the CRC algorithm is used to check the correspondence between each pin and its pin type. This new method has a high accuracy and a low execution time. It can meet the crucial timing requirement of a high-speed SMT machine through experimental verification.

This paper synthesizes an efficient walking pattern for a practical biped robot when ascending and descending stairs. The main features of the biped robot include variable length legs and a translatable balance weight in the body. The biped robot's walk is a mixture of both statically stable and dynamically stable modes and relies on some degrees of static stability provided by large feet and by carefully controlling the center of gravity's position. The paper describes the design and experiment of a 7-DOF practical biped which is capable of ascending and descending stairs, and the synthesis of an efficient walking gait for ascending and descending stairs. Our biped robot is one of the few biped walking machines capable of ascending and descending stairs.

This work studies the motion control of a statically stable biped robot having seven degrees of freedom. Statically stable walking of the biped robot is realized by maintaining the center-of-gravity inside the convex region of the supporting foot and/or feet during both single-support and double-support phases. The main points of this work are framing the stability in an easy and correct way, the design of a bipedal statically stable walker, and walking on sloping surfaces and stairs.

This paper studies the dynamics of a biped walking robot with seven degrees of freedom. The main features of the biped robot include variable length legs and a translatable balance weight in the body. Dynamically stable walking of the biped robot is realized by maintaining the zero moment point (ZMP), which is the virtual total ground reaction point, within the region of the supporting foot during the single-support phases. An implementation of prototype biped BR-1 and its experimental walking test results are described. On a flat plane, the biped can walk dynamically with a speed of 16 cm/second.

An adaptive gait algorithm for multilegged walking machines over rough terrain has been developed. The heuristic and hierarchical approach for the three levels of: 1) body motion adaptation; 2) leg sequence adaptation; and 3) leg position adaptation is effective, straightforward, and relatively independent of the number of legs. On rough terrains with depressions the algorithm behaves like a "free gait"; on level ground terrain it behaves more like a periodic gait. The effectiveness of the proposed gait over rough terrains with depressions is demonstrated with several computer simulations.>

The development and implementation of an advanced control system for a seven-link, 12-degree-of-freedom, biped robot in the double-support phase are addressed. A constrained dynamic model of the biped robot is formulated and a reduced order model for the double-support phase is derived. In this model the dependent variables are related to the independent variables through the kinematic Jacobian. Control strategies based on feedforward compensation and linear state feedback are derived for tracking specified joint trajectories. The approach is demonstrated using results of a sway motion obtained from a prototype biped robot that has been constructed.>

A method for planning collision-free trajectories of two SCARA robots in a common workspace is described. The robots are treated as a single redundant system. A collision map representing the intersection of the robots is developed in a two-parameter space. A trajectory is planned by finding a collision-free path in the parameter space as a primary constraint and minimizing an objective function in joint space as a secondary goal. An artificial potential field facilitates path planning in the parameter space. A gradient projection method minimizes the error between the current and desired joint angles and optimizes other criteria. The proposed formulation has application in flexible assembly cells which utilize multiple SCARA robots. Two examples demonstrate the effectiveness of the method.>

The synthesis and verification of biped walking trajectories during the single-support phase is discussed. The biped is modeled as a seven-link twelve degree-of-freedom anthropomorphic robot. By utilizing the zero moment point (ZMP) and the equivalent force-moment, the physical admissibility of the biped walking is characterized. For physically realizable walking during the single-support phase, the trajectory of the ZMP on the ground must be inside the stable region of the supporting sole. A biped walking trajectory specified by eight pattern parameters is derived through inverse kinematics. ZMP trajectories for different walking patterns and the influence of the pattern parameters on the ZMP trajectories are presented.>

A method is presented for path planning of a point robot moving among polyhedral obstacles with piecewise constant translating velocity. Representing the obstacles as polyhedra in the space-time domain allows a collision-free, minimum-time path to be obtained using graph search and linear programming. The planner views the space-time configuration of free space as disjoint polytopes where each point in the space-time domain is mapped into a unique polytope. The planner searches connected polytopes between the start and goal polytopes that satisfy the speed and time constraints. A near-optimal trajectory is determined by constrained optimization. In the proposed approach, the obstacle is allowed to move faster than the point robot, and the methodology can be easily extended to motion planning in higher-dimensional spaces.>

A unified approach suitable for path planning with moving polyhedral obstacles is presented. The planner views the space-time configuration of free space as disjoint polytopes that represent a time-dependent environment consisting of moving and stationary objects. Each point in the space-time domain is mapped into a unique polytope set. The planner then constructs a family of feasible collision-free trajectories by searching connected polytopes between the start polytope and the goal polytope that satisfy the speed and time constraints. Finally, a near-optimal trajectory is determined by constrained optimization. This approach does not require that obstacles be nonoverlapping or noncolliding. In addition, the obstacle is allowed to move faster than the planned robot. However, the speed of the obstacle must be piecewise-constant. The proposed approach can be easily extended to motion planning in higher dimensional spaces.>

Some of the fundamental problems of the gait control of a quadruped walking vehicle are addressed. It is shown that the product of the duty factor and the stride length is equal to the length of the boundary of the reachable area of the leg. Furthermore, the mathematical expression representing the relationship between the stability margin, the stride length and duty factor are also formulated. These equations are expressed in terms of quantities that specify the configuration of the quadruped walking vehicle. Based on the derived results, a graphical approach to determine the required stride length and the duty factor that corresponding to a regular gait with a prescribed static stability margin is presented. This graphical approach is then adopted to determine the regular gait of a quadruped walking vehicle, and the results agree with the analytic approach.