Quadruped Walking Research Articles

2P1-K09 油圧式4脚ロボットRL-R1の機構設計と脚部の試作

This paper reports on a hydraulic quadruped walking robot, which is designed for the prototype of leg wheel type robot RL-R1. The legs are operated by hydraulic cylinders and rotary actuators. The range of motion and joint torque are set aiming at forest operations or disaster response. We achieved lightweight and high strength leg by using carbon fiber reinforced plastic. This paper shows some preliminary experimental results including squat motion under 165 kg payloads and swing motion at maximum speed. As a result, the developed legs are confirmed to have sufficient torque and strength for our mission.

2A1-V05 脚-車輪ハイブリッド移動体に搭載する周辺環境計測システムの研究

This paper explains a development of an environment measuring system mounted on leg-wheel hybrid vehicle for rescue mission. Recently, there are many studies of rescue robots reported in various conferences in the world wide. The most robots aim at searching victims of some disaster. This study also aims to development of a rescue robot based on a quadruped walking robot, although the most rescue robots are crawler-type. The quadruped walking robot is equipped with rollers at the tip of the each leg. It performs roller-skates on a flat ground movement by utilizing the flexibility of the legs and walks on rough terrain as a walking. This paper also shows the three-dimensional maps as results of the 3D scanning experiments with Laser Range Finder mounted on the robot.

Age- and sex-based patterns of positional behavior and substrate utilization in the golden snub-nosed monkey (Rhinopithecus roxellana).

Body mass plays an important role in primate positional behavior and in sexually dimorphic arboreal primate species may influence how immature and adult individuals travel through the forest canopy and access food resources. In this study, we examined age- and sex-based patterns of positional behavior and substrate utilization in wild golden snub-nosed monkeys (Rhinopithecus roxellana), an endangered species of Asian colobine. Our results indicated that among all age and sex classes, sitting was the most common feeding and resting posture and during travel, quadrupedal walking was the dominant locomotor behavior. Despite the fact that adult male R. roxellana are reported to exhibit a body mass nearly two times that of adult females, we found no significant sex differences in the positional repertoire during feeding and traveling. In addition, we found that while infants and juveniles used similar postural and locomotor behaviors as their adult counterparts, younger golden snub-nosed monkeys more frequently engaged in risky or escape-oriented behaviors such as climbing, running, leaping, and forelimb suspension. With increasing age, the use of quadrupedal walking and dropping (downward in-air displacement of body mass that does not require hindlimb propulsion) increased and the use of leaping, suspensory postures, and bridging decreased. Finally, given differences in the positional repertoire of adult and immature golden snub-nosed monkeys, we argue that studies of ontogenetic patterns of positional behavior should emphasize what it takes to survive at each life stage rather than what it takes to match an adult repertoire.

Electronic bypass of spinal lesions: activation of lower motor neurons directly driven by cortical neural signals.

BackgroundLower motor neurons in the spinal cord lose supraspinal inputs after complete spinal cord injury, leading to a loss of volitional control below the injury site. Extensive locomotor training with spinal cord stimulation can restore locomotion function after spinal cord injury in humans and animals. However, this locomotion is non-voluntary, meaning that subjects cannot control stimulation via their natural “intent”. A recent study demonstrated an advanced system that triggers a stimulator using forelimb stepping electromyographic patterns to restore quadrupedal walking in rats with spinal cord transection. However, this indirect source of “intent” may mean that other non-stepping forelimb activities may false-trigger the spinal stimulator and thus produce unwanted hindlimb movements.MethodsWe hypothesized that there are distinguishable neural activities in the primary motor cortex during treadmill walking, even after low-thoracic spinal transection in adult guinea pigs. We developed an electronic spinal bridge, called “Motolink”, which detects these neural patterns and triggers a “spinal” stimulator for hindlimb movement. This hardware can be head-mounted or carried in a backpack. Neural data were processed in real-time and transmitted to a computer for analysis by an embedded processor. Off-line neural spike analysis was conducted to calculate and preset the spike threshold for “Motolink” hardware.ResultsWe identified correlated activities of primary motor cortex neurons during treadmill walking of guinea pigs with spinal cord transection. These neural activities were used to predict the kinematic states of the animals. The appropriate selection of spike threshold value enabled the “Motolink” system to detect the neural “intent” of walking, which triggered electrical stimulation of the spinal cord and induced stepping-like hindlimb movements.ConclusionWe present a direct cortical “intent”-driven electronic spinal bridge to restore hindlimb locomotion after complete spinal cord injury.

Central pattern generator based reflexive control of quadruped walking robots using a recurrent neural network

This paper presents a novel Central Pattern Generator (CPG) model for controlling quadruped walking robots. The improvement of this model focuses on generating any desired waveforms along with accurate online modulation. In detail, a well-analyzed Recurrent Neural Network is used as the oscillators to generate simple harmonic periodic signals that exhibit limit cycle effects. Then, an approximate Fourier series is employed to transform those mentioned simple signals into arbitrary desired outputs under the phase constraints of several primary quadruped gaits. With comprehensive closed-form equations, the model also allows the user to modulate the waveform, the frequency and the phase constraint of the outputs online by directly setting the inner parameters without the need for any manual tuning. In addition, an associated controller is designed using leg coordination Cartesian position as the control state space based on which stiffness control is performed at sub-controller level. In addition, several reflex modules are embedded to transform the feedback of all sensors into the CPG space. This helps the CPG recognize external disturbances and utilize inner limit cycle effect to stabilize the robot motion. Finally, experiments with a real quadruped robot named AiDIN III performing several dynamic trotting tasks on several unknown natural terrains are presented to validate the effectiveness of the proposed CPG model and controller.

Planning and Simulation of the Rule-Based Trotting Gait of a Bionic Quadruped Robot

In order to make the quadruped robot walk stably with trotting gait, this paper analyzed the animal's motion to get the rule-based gait sequences and used the half wave functions and cosine functions to plan the functions of every joint combining cyclical motion. Also, on the basis of the obtained gait, the virtual prototype of a bionic quadruped robot was established and kinematic and dynamic simulations were done. The simulation results show that the motion functions can make virtual prototype of the quadruped robot walk stably and the rule-based gait planning method is accurate and reasonable.

A dynamic model of an underwater quadruped walking robot using Kane’s method

In this paper, the kinematics and dynamics of an underwater quadruped walking robot were derived based on Kane dynamic equations. This methodology allows construction of the dynamic model simply and incrementally. The velocity and angular velocity components of an underwater quadruped walking robot were served as the generalized velocities. The forces which contribute to dynamics of an underwater quadruped walking robot were determined by Kane’s approach. The equations of hydrodynamic forces of an underwater quadruped walking robot were deduced. Hydrodynamic coefficients were determined by experiments. The dynamic model was established by obtaining the generalized active forces and the generalized inertia forces. Numerical simulations of the walking behavior on underwater flat ground were implemented to verify the dynamic model of an underwater quadruped walking robot. Simulation results show that the dynamic model is correct.

Dynamic Simulation of Hydraulic Driving Mechanism Based on ADAMS

It establishes the model of hydraulic driving quadruped walking robot by Lagranges equation according to mechanism parameter. It determines the relationship between joint space and operating space. Comprehensive using the software Pro/E and ADAMDS, then build its virtual model and present dynamics simulation. It analyses the robots walking tracks and stability of motion. It provides theory reference for optimized out reasonable quadruped walking robots structure parameter.

Cam Drive Step Mechanism of a Quadruped Robot

Bionic quadruped robots received considerable worldwide research attention. For a quadruped robot walking with steady paces on a flat terrain, using a cam drive control mechanism instead of servomotors provides theoretical and practical benefits as it reduces the system weight, cost, and control complexities; thus it may be more cost beneficial for some recreational or household applications. This study explores the robot step mechanism including the leg and cam drive control systems based on studying the bone structure and the kinematic step sequences of dog. The design requirements for the cam drive robot legs have been raised, and the mechanical principles of the leg operating mechanism as well as the control parameters have been analyzed. A cam drive control system was constructed using three cams to control each leg. Finally, a four-leg demo robot was manufactured for experiments and it showed stable walking patterns on a flat floor.

1A1-P06 高い対地適応性を有する4脚歩行機械のための脚自由度構成に関する研究(脚移動ロボット)

1A1-P06 高い対地適応性を有する4脚歩行機械のための脚自由度構成に関する研究(脚移動ロボット)

Development of quadruped walking robot TITAN XII and its basic consideration on the control of large obstacle traversing motion

Quadruped walking robots are expected to be utilized for various works on rugged terrain because it has minimum leg number to maintain static stability during walking motion and it can demonstrate high terrain adaptability by utilizing its high degrees of freedom. For these reasons, it has been studied for a long time. However, the study about traversing on rugged terrain by quadruped walking robot has not been done enough yet. In this paper, both basic strategy of motion control and mechanical design of a quadruped walking robots for large obstacle climbing are considered. In order to establish the basis of the control of quadruped walking robots to achieve large obstacle traversing motion with high energy efficiency, we make simulation experiments about body rising motion which essentially requires positive power consumption. We investigate the appropriate foot positions and internal forces which eliminate negative power consumption at the joint, then optimize the motion in consideration of characteristics of the installed actuators. Furthermore, a quadruped walking robot to go over large obstacle named“TITAN XII ”is proposed and its design concept and system integration are discussed. Finally, validity of simulation results and basic performance of TITAN XII are confirmed by experiments.

Development of quadruped walking locomotion gait generator using a hybrid method

The earth, in many areas is hardly reachable by the wheeled or tracked locomotion system. Thus, walking locomotion system is becoming a favourite option for mobile robot these days. This is because of the ability of walking locomotion to move on the rugged and unlevel terrains. However, to develop a walking locomotion gait for a robot is not a simple task. Central Pattern Generator (CPGs) method is a biological inspired method that is introduced as a method to develop the gait for the walking robot recently to tackle the issue faced by the conventional method of pre-designed trajectory based method. However, research shows that even the CPG method do have some limitations. Thus, in this paper, a hybrid method that combines CPG and the pre-designed trajectory based method is introduced to develop a walking gait for quadruped walking robot. The 3-D foot trajectories and the joint angle trajectories developed using the proposed method are compared with the data obtained via the conventional method of pre-designed trajectory to confirm the performance.

Dynamics of a Quadruped Walking Machine

The purpose of this study is to propose a new quadruped walking machine and investigate its dynamics. This paper first proposes a new quadruped walking machine and introduces its structure. The basic theory behind the equation of motion is briefly introduced. The dynamic characteristics of the walking machine, including the position, velocity, acceleration, support leg sequence, foot trajectory and pitch angle, are investigated and compared with the existing design. The results show that better transmission efficiency is achieved when the driving torque of the walking machine acts on the shaft of the crank. Compared to the existing design, the design proposed in this study has fewer changes in pitch angle during movement and exhibits less skidding while changing support leg.

Bipedal and quadrupedal locomotion in chimpanzees

Chimpanzees (Pan troglodytes) habitually walk both bipedally and quadrupedally, and have been a common point of reference for understanding the evolution of bipedal locomotion in early ape-like hominins. Here we compare the kinematics, kinetics, and energetics of bipedal and quadrupedal walking and running in a sample of five captive chimpanzees. Kinematics were recorded using sagittal-plane digital high-speed video of treadmill trials. Kinetics were recorded via a forceplate. Metabolic energy cost was measured via steady-state oxygen consumption during treadmill trials. Consistent with previous work on chimpanzees and other hominoids, we found that the spatiotemporal characteristics, joint angles, ground reaction forces, and metabolic cost of bipedal and quadrupedal locomotion are similar in chimpanzees. Notable differences include hip and trunk angles, which reflected a more orthograde trunk posture during bipedalism, and mediolateral ground reaction forces, which were larger during bipedal walking. Stride frequencies were also higher (and step lengths shorter) during bipedal trials. Bipedal and quadrupedal walking among chimpanzees was similar to that reported for bonobos, gibbons, and other primates. The similarity in cost between bipedal and quadrupedal trials suggests that the adoption of bipedal walking would have had no effect on walking costs for early ape-like hominins. However, habitual bipedalism may have favored modifications of the hip to allow a more orthograde posture, and of the hind limb abductor mechanisms to efficiently exert mediolateral ground forces.

Development of a quadruped walking robot AiDIN-III using biologically inspired kinematic analysis

This paper presents a bio-inspired mechanism design for a quadruped walking robot. The approach is derived from the observation on the behaviors of quadruped locomotion, skeletal structure, and the study on the stability of walking based on morphological analysis. In the first, we define the design parameters such as the dimensions of the body and limbs, the center of mass position, and locomotion mechanisms based on surveys on the literatures from biologists. Then, by using the parameters, we propose an useful framework for determining the design parameters of a quadruped walking robot. For implementations, we manufacture a dog-type self-contained quadruped walking robot, named AiDIN-III (Artificial Digitigrade for Natural Environment version III) and the effectiveness of the proposed idea is validated via experimental works.

Magnetorheologically Damped Compliant Foot for Legged Robotic Application

This paper presents an innovative solution for bounce reduction between a robotic leg and the ground by means of a semi-active compliant foot. The aim of this work is to enhance the controllability and the balance of a legged robot by improving the traction between the foot tip and the ground. The compliant foot is custom-designed for quadruped walking robots and it consists of a linear spring and a magnetorheological (MR) damper. By utilizing magnetorheological technology in the damper element, the damping coefficient of the compliant foot can be altered across a wide range without any additional moving parts. The content of this paper is twofold. In the first part the design, a prototype and a model of the semi-active compliant foot are presented, and the performance of the magnetorheological damper is experimentally studied in quasi-static and dynamic cases. Based on the quasi-static measurements, the damping force can be controlled in a range from 15 N to 310 N. From the frequency response measurements, it can be shown that the controllable damping force has a bandwidth higher than 100 Hz. The second part of this paper presents an online stiffness identification algorithm and a mathematical model of the robotic leg. A critical damping control law is proposed and implemented in order to demonstrate the effectiveness of the device that makes use of smart materials. Further on, drop tests have been carried out to assess the performance of the proposed control law in terms of bounce reduction and settling time. The results demonstrate that by real-time control of the damping force 98% bounce reduction with settling time of 170 ms can be achieved.

Locomotor and postural development of wild chimpanzees

Chimpanzees are our closest living relatives and their positional repertoire likely includes elements shared with our common ancestor. Currently, limitations exist in our ability to correlate locomotor anatomy with behavioral function in the wild. Here we provide a detailed description of developmental changes in chimpanzee locomotion and posture. Fieldwork was conducted on wild chimpanzees at Ngogo, Kibale National Park, Uganda. The large size of the Ngogo chimpanzee community permitted cross-sectional analysis of locomotor and postural changes across many individuals. Chimpanzee positional behavior proceeds developmentally through a number of distinct stages, each characterized by its own loading regime. Infants principally used their upper limbs while moving; the loading environment changed to more hindlimb dominated locomotion as infants aged. Infants displayed more diversity in their forms of positional behavior than members of any other age-sex class, engaging in behaviors not habitually exhibited by adults. While the most common locomotor mode for infants was torso-orthograde suspensory locomotion, a large shift toward quadrupedal locomotion during infancy occurred at three years of age, when rates of this behavior increased. Overall, the most dramatic transition in positional behavior occurred during juvenility (at approximately five years), with the advent of complete independent locomotion. Juveniles decreased the amount of time they spent clinging and in torso-orthograde suspensory locomotion and increased their time spent sitting and walking and running quadrupedally compared with younger individuals. Juvenility marked the age at which quadrupedal walking became the most frequent locomotor behavior, but quadrupedal walking did not encompass the majority of locomotor time until individuals reached adolescence. Relative to all younger individuals, adolescent chimpanzees (10–13 years) experienced a further increase in the amount of time they walked quadrupedally. Locomotor behavior did not reach adult form until adolescence, closer to the time of epiphyseal fusion than previously thought. These findings provide new data to make predictions about how behavioral transitions influence skeletal change.

Design and Analysis of the Quadruped Walking Robot Based on 3-RPS Parallel Mechanism

Based on the importance of the robot for the elderly and the disabled, a quadruped walking robot using 3-RPS parallel mechanism as the basic leg mechanism is proposed. The structure of the basic leg is described, and the whole structure of the quadruped walking robot is formed. Then taking the workspace of the basic leg as the standard, the optimum size parameters of the upper platform and the lower platform of the based leg are achieved. Meanwhile the workspace of the basic leg is obtained by the anti-solution search method. Taking the basic leg as analysis object and applying the virtual organization method, the kinematic expression is got. All of these analyses lay a theoretical foundation for the further study on the quadruped walking robot with parallel leg mechanism.

Brief communication: Swimming and diving behavior in apes (Pan troglodytesandPongo pygmaeus): First documented report

Extant hominoids, including humans, are well known for their inability to swim instinctively. We report swimming and diving in two captive apes using visual observation and video recording. One common chimpanzee and one orangutan swam repeatedly at the water surface over a distance of 2-6 m; both individuals submerged repeatedly. We show that apes are able to overcome their negative buoyancy by deliberate swimming, using movements which deviate from the doggy-paddle pattern observed in other primates. We suggest that apes' poor swimming ability is due to behavioral, anatomical, and neuromotor changes related to an adaptation to arboreal life in their early phylogeny. This strong adaptive focus on arboreal life led to decreased opportunities to interact with water bodies and consequently to a reduction of selective pressure to maintain innate swimming behavior. As the doggy paddle is associated with quadrupedal walking, a deviation from terrestrial locomotion might have interfered with the fixed rhythmic action patterns responsible for innate swimming.

Universal Multiaxis Control System for Electric Drives

This paper presents a solution for universal multidrive control system, which can be used as a base for the rapid prototyping of various kinematic structures, particularly in robotics, for multiple-axis synchronization tasks, or as a test bed for verification of modern control algorithms for electric drives. The example of the practical application of the proposed system was also given: It was used during prototyping process of a quadruped walking robot, powered by multiple electric motors. The abilities and performance of the system were verified with the attempt to realize the dynamic gait of the robot.