Noriho Koyachi

Planning walking patterns for a biped robot

Biped robots have better mobility than conventional wheeled robots, but they tend to tip over easily. To be able to walk stably in various environments, such as on rough terrain, up and down slopes, or in regions containing obstacles, it is necessary for the robot to adapt to the ground conditions with a foot motion, and maintain its stability with a torso motion. When the ground conditions and stability constraint are satisfied, it is desirable to select a walking pattern that requires small torque and velocity of the joint actuators. We first formulate the constraints of the foot motion parameters. By varying the values of the constraint parameters, we can produce different types of foot motion to adapt to ground conditions. We then propose a method for formulating the problem of the smooth hip motion with the largest stability margin using only two parameters, and derive the hip trajectory by iterative computation. Finally, the correlation between the actuator specifications and the walking patterns is described through simulation studies, and the effectiveness of the proposed methods is confirmed by simulation examples and experimental results.

A high stability, smooth walking pattern for a biped robot

Biped robots have better mobility than conventional wheeled robots, but they tip over easily. In order to walk stably in various environments such as rough terrain, up and down slopes, or regions containing obstacles, it is desirable to adapt to such ground conditions with a suitable foot motion, and maintain the stability of the robot by a smooth hip motion. We propose a method to plan a walking pattern consisting of a foot trajectory and a hip trajectory. First, we formulate the constraints of a foot trajectory, and generate the foot trajectory by 3rd order spline interpolation. By setting the values of constraint parameters, it is easy to produce different types of foot motion. Then, we formulate a hip trajectory using a 3rd order periodic spline function, and derive the hip trajectory with high stability. Finally, the effectiveness of the proposed method is illustrated by simulation examples.

Balance control of a piped robot combining off-line pattern with real-time modification

Since a biped robot tends to tip over easily, stable and reliable biped walking is a very important achievement. In this paper, we propose a balance control method based on an off-line planned walking pattern with real-time modification. First, a method of generating a highly stable, smooth walking pattern is presented. Then, a method of real-time modification consisting of body posture control, actual zero moment point control and landing time control based sensor information is proposed. By combining the proposed off-line walking pattern with real-time modification, the biped robot can walk smoothly and adapt to unknown environments. The effectiveness of the proposed method is confirmed by dynamic simulator such as walking on unexpected irregular rough terrain, soft ground and in environments in the presence of disturbances.

Kinematic analysis of translational 3-DOF micro parallel mechanism using matrix method

We apply the matrix method to kinematic analysis of our translational 3-DOF micro parallel mechanism for an instance of general flexure mechanisms. The matrix method has been well developed in architecture to analyze a frame structure. We found that this method is well applicable to such a flexure mechanism with circular notched hinges as our micro parallel mechanism because it is approximate to the Rahmen structure. Our matrix method can calculate a compliance matrix with less nodes of matrix than conventional finite element method. First, the compliance matrices of a circular notched hinge and some other beams are defined and the coordinate transformations of compliance matrix are introduced. Next, an analysis of our micro parallel mechanism is demonstrated.

Development of small-sized 3 DOF finger module in micro hand for micro manipulation

A dexterous micro manipulation system was developed for applications such as assembling micro machines, manipulating cells, and micro surgery. We have proposed a concept of a two-fingered microhand, and designed and built a prototype. We succeeded in performing basic micro manipulations, including the grasp, release, and rotation of a microscopic object. The two-fingered micro hand prototype should be more miniaturized for higher accuracy and combination in small chamber of SEM. In this paper, we will propose a small-sized 3-DOF finger module with a parallel mechanism. An optimized link mechanism for miniaturization is used to the finger module. A photo fabrication system is used to fabrication of the finger module. Basic experiment shows excellent micro capability.

Mechanism and control of a leg-wheel hybrid mobile robot

Describes the mechanism and control of a leg-wheel hybrid mobile robot. Legged locomotion has high adaptability for rough terrain, and wheeled locomotion possesses speed and efficiency. A locomotion mechanism that combines legs and wheels is proposed, and a prototype mobile robot that adopts the mechanism is introduced. The robot has four legs, and a wheel is attached at the end of each leg. The front leg has three joints and a passive wheel. The rear leg has one joint and an active wheel. In order to make the best of the mechanism, three locomotion modes, wheel mode, hybrid mode, and step mode, are developed. In the wheel mode, four wheels are used on flat terrain. On rough terrain, the hybrid mode is selected, and two legs and two active wheels are used for locomotion. To climb or descend a large step, the step mode is used.

Kinematic analysis of a translational 3-d.o.f. micro-parallel mechanism using the matrix method

In this paper, we applied the matrix method to kinematic analysis of our translational 3-d.o.f. micro-parallel mechanism for an instance of general flexure mechanisms. The matrix method has been well developed in architecture to analyze frame structures. We found that this method is well suited to such a flexure mechanism with circular notched hinges as our micro-parallel mechanism because it can be approximated to a Rahmen structure. Our matrix method can calculate a compliance matrix with less matrix nodes than the conventional finite element method. First, the compliance matrices of a circular notched hinge and some other beams are defined, and the coordinate transformations of the compliance matrix are introduced. Secondly, an analysis of our micro-parallel mechanism is demonstrated.

Robotic Assist for MR-Guided Surgery Using Leverage and Parallelepiped Mechanism

In this paper, we would propose a novel mechanism of surgical manipulator, which assists the surgeon in precise positioning and handling of surgical devices, like biopsy needle, endscope, in MR-guided surgery. This mechanism can transmit 3 translational and 3 rotational motion from the outside to the inside of MR imaging area using leverage and parallelepiped mechanism. Such a remote actuation is significantly helpful for robotic assist under MR-guided surgery because the strong magnet of MR denies the existence of magnetic and electric devices around imaging area. This mechanism also has merits of the mechanical safety and simple shape. The combination of stereotactic imaging and precise positioning would enable a less invasive surgery in brain and spine surgery.

A hybrid drive parallel arm for heavy material handling

This article discusses a hybrid drive parallel arm driven by cables and cylinders in order to design a compact handling arm, thus enlarging its workspace. Our major objective is to develop a dexterous arm capable of controlling six-degree-of-freedom (DOF) motion of heavy materials. The article includes a basic concept of parallel mechanisms with hybrid actuation, comparisons and evaluations of some types of hybrid mechanisms based on its kinematics and statics, and finally introduces a designed prototype arm.

Force control system for autonomous micro-manipulation

A dexterous micro-manipulation system was developed for applications such as assembling micro-machines, manipulating cells, and micro-surgery. We proposed a concept of a two-fingered micro-hand, and designed and built a prototype. We succeeded in performing basic micro-manipulations, including the grasp, release, and rotation of a microscopic object. The micro-hand is controlled by a position controller only. The accuracy of the micro-manipulation depends on the skill of the operator. For automatic manipulation, it is necessary to measure the micro-forces between the finger and the object. A micro force sensor has developed for the force control in micro-manipulation. In this paper, we describe the micro force sensor and perform an automatic micro-manipulation and force control with the sensor. The basic experiment performed shows excellent micro-capability.