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Zhao W.,Northwestern Polytechnical University | Zhao W.,Shaanxi Province Digital Special Manufacturing Equipment Engineering Research Center | Wang R.,Shaanxi Province Digital Special Manufacturing Equipment Engineering Research Center | Zhang X.,Shaanxi Province Digital Special Manufacturing Equipment Engineering Research Center | Wang X.,Yulin University
2015 IEEE International Conference on Robotics and Biomimetics, IEEE-ROBIO 2015 | Year: 2015

It is well-known that SLIP model is one of the best and simplest abstractions describing the dynamics of hopping and running in animal and human locomotion. Nevertheless, spring-like leg behavior depends on the compliance of limb multiple joints in animal and human locomotion. Therefore, we investigate the influence of biological joint stiffness on running stability based on two-segment leg model. A nonlinear relationship between the virtual leg spring force and the virtual leg spring compression is found because of a nonlinear biological joint torque-angular displacement relationship of elastic two-segment leg. The functional relationship between the virtual leg spring force and the virtual leg spring compression is established, and then based on biological limbs maximum compression in fast running, we establish the equation for solving the radius of cable pulley. At high speed the tolerated minimum dimensionless reference stiffness in two-segment leg model is largely decreased (17 at 29 m s-1, β0=110°) compared with linear leg spring model (45). In fast locomotion, the two-segment leg model with biological joint stiffness can demonstrate outstanding performance for stable running. © 2015 IEEE. Source


Qin X.,Northwestern Polytechnical University | Qin X.,Shaanxi Province Digital Special Manufacturing Equipment Engineering Research Center | Zhang X.,Northwestern Polytechnical University | Tan X.,Northwestern Polytechnical University | And 2 more authors.
Zhongguo Jixie Gongcheng/China Mechanical Engineering | Year: 2013

For discrete ground contact, there were high adaptability and extensive application prospect for mammalian legged robot when encountering special topographical and unpredictable environment such as obstacles, ditch and so on. This paper surveyed the development process of mammalian legged robots, and mainly introduced overseas and domestic research status in terms of two legged and four legged robots. The related theory and method on legged structure, joint drive, navigation, stability criterion and control algorithm were analyzed and discussed, Meanwhile, the difficulties to be solved under development were analyzed and the future of legged robots was forecasted. Source


Liu A.,Northwestern Polytechnical University | Liu A.,Shaanxi Province Digital Special Manufacturing Equipment Engineering Research Center | Wu H.,Northwestern Polytechnical University | Wu H.,Shaanxi Province Digital Special Manufacturing Equipment Engineering Research Center | Li Y.,Northwestern Polytechnical University
2013 IEEE International Conference on Robotics and Biomimetics, ROBIO 2013 | Year: 2013

In this paper, a gait transition method of quadruped robot was investigated, which is controlled by changing rhythm. It makes the duration time of liftoff and touchdown events variable through the continuous change of walking parameters, and realizes the gait transition from walk to trot. The quadruped bionic robot is a series parallel-multiple branching of nonlinear inverted pendulum system. The stability of trot gait in gait transition processes to the stability of inverted pendulum, and the balance adjustment is generated basing the original motion. The experiment is verified by interactive co-simulation among Matlab-Adams. The transition method satisfies the continuous and steady movement of quadruped robot in gait transition. © 2013 IEEE. Source


Liu A.,Northwestern Polytechnical University | Liu A.,Shaanxi Province Digital Special Manufacturing Equipment Engineering Research Center | Zhang X.Y.,Northwestern Polytechnical University | Zhang X.Y.,Shaanxi Province Digital Special Manufacturing Equipment Engineering Research Center | And 2 more authors.
Applied Mechanics and Materials | Year: 2013

The adaptability of velocity changing of quadruped robot needs to be realized by gait transition. In this paper, a gait transition method of a quadruped robot based on changing the time sequence was investigated. The swing phase and the stance phase are separated by finite-state machine (FSM), and the locomotion gait involves breaking/enforcing synchronization or changing the order of leg liftoff events, it makes the duration time of liftoff and touchdown events variable. The gait transition from walk to trot is realized by the combination driving of time and event. The experiment is verified by interactive co-simulation among Matlab-Adams. The transition method satisfies the velocity changing of quadruped robot. © (2013) Trans Tech Publications, Switzerland. Source


Li J.,Northwestern Polytechnical University | Li J.,Shaanxi Province Digital Special Manufacturing Equipment Engineering Research Center | Zhang X.Y.,Northwestern Polytechnical University | Zhang X.Y.,Shaanxi Province Digital Special Manufacturing Equipment Engineering Research Center | And 4 more authors.
Applied Mechanics and Materials | Year: 2013

In quadruped robot, there is the strong correlation of kinematic parameters for the joints of two-section leg, and it is difficult to realize the decoupling of rhythm and pattern over rough terrains. In this paper, we investigated the physiological feature, locomotion characteristics and main function of shoulder blade of quadrupeds, and based on the results, we proposed a stratified control system on the three-section leg to realize better adaptation of a robot to terrains. Through the active control of shoulder blade (frequency and amplitude) and the coupled passive control of upper arm and forearm, a leg may adjust to the terrains of different elevations without changing the movement state of shoulder blade and body speed. In addition, the foot trajectory was planned and a rough terrain was created for testing the athletic ability of a three-section leg, and the validity of the proposed control system is confirmed through simulation. © (2013) Trans Tech Publications, Switzerland. Source

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