6축 머니퓰레이터를 이용한 임피던스 제어 기반의 원형 펙 조립

This paper proposes an intelligent massage control system by using multi-fingered robot hand with hybrid impedance and force control, which is able to create the movement and force of robot to behave as similar as the human’s massage. Therefore, the various massage points, such as the changing of hardness and softness of human skin muscle condition, can be appropriately controlled by using hybrid impedance and force control method. The impedance control is used to control the lateral position of massage on the human skin muscle. The perpendicular direction one, while force control is carried out for the vertical direction on human skin muscle. This paper also gives a modeling of human skin muscle through robot perception of impedance to decide the parameter of impedance controller. The control strategy using a hybrid impedance and force control to implement an adaptive control system is presented, when human condition is changed with soft and hard skin muscle. For the robot fingertip force, PI servo compensation is used together with impedance control. Based on using both impedance and PI servo compensation, the effectiveness of the massage position and force control is shown through actual massage motion experiments.

The best exoskeleton control strategy depends on the task, motivating the development and analysis of an exoskeleton capable of position, force, and impedance control. In this paper, we implement and compare the three controller types via sliding mode control on a custom-built pneumatic cylinder ankle exoskeleton. To evaluate each controller's performance, the exoskeleton was tested on the benchtop and with human subject experiments. With the position controller, the exoskeleton achieved an root-mean-square error (RMSE) of under 5 deg for both the benchtop and human tests. It had a bandwidth of approximately 12 rad/s. The force controller tracked sinusoidal trajectories acceptably well at low frequencies (15% of force range at 6 rad/s), with a bandwidth of approximately 24 rad/s. The error was significantly higher (RMSE of 24% of force range) for the more biologically relevant trajectory. The impedance controller demonstrated the desired spring-like behavior, with position RMSE generally under 5 deg compared to expected position. All three controllers worked equally well for benchtop and human tests. Thus, a pneumatically powered ankle exoskeleton with sliding mode control is capable of accurate position and impedance control and is capable of marginally acceptable force control.

In this paper, a novel impedance control method is designed for the hydraulic drive unit (HDU) equipped on the hydraulic driven legged robot. First, the position control mathematical model of HDU is built. Next, the HDU performance test platform is introduced and the performance requirements are given. Second, the system load pressure observer is designed and an accurate stiffness control method is proposed by combining the external load force feed forward control with the load force feedback control. Third, the damping control method based on the velocity feedback is designed. Finally, a novel impedance control method is proposed through combining the stiffness control and the damping control. The effects of all techniques listed above have been verified experimentally. Especially, the impedance control effects are verified by comparing the impedance characteristics with the natural characteristics of the second-order mass-spring-damper system. This research indicates that the system characteristics of HDU with the novel impedance control method is well equivalent to that of the second-order mass-spring-damper system, which can solve the stall problem of the robot joint movement process caused by the load force vanish instantaneously and the switch between position control and force control. The above research can provide references for the active compliance control of bionic legged robots.

Two different control schemes, position model referenced control (PMRC) and force model referenced control (FMRC), are developed for a simplified two robots model with one interacting axis. The dynamic stability of the position (or force) control under the FMRC (or PMRC) is analyzed. Results indicate that PMRC, although providing better dynamic performance of the position control, may degrade the dynamic performance of the force control. However, FMRC can provide better dynamic performance of both position and force control.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A walking assistance apparatus which can promote gait training for motor palsy patients and outdoor walking for the elderly was developed. Our prototype uses a novel spatial parallel link mechanism and restraint free type of equipment. The apparatus supports complete leg alignment, including the soles of the feet from under the soles with flat steps, and assists walking behavior at the ankle, knee, and hip joints simultaneously without the use of Velcro tape. We proposed the control method according to the purpose of the user. For example, to promote gait training, this apparatus can select the impedance control method. User's legs are assisted along the trajectory with the ideal gait as well as walking. To promote outdoor walking for the elderly, this apparatus can select the torque control method. The apparatus calculates the necessary torques of each joint according to the posture and motion of the apparatus and user. In the case of the impedance control method, by adjusting the natural frequency of the ideal dynamic equation for the flat steps under the soles, the user felt it was easier to walk by frequency entrainment. On the other hand, to promote outdoor walking of the user, this apparatus has to be used not only on the flat ground but also on stairs or slopes with freedom behaviors, and it has to make the user feel comfortable. To address this problem, the torque control method proposed to use real-time acceleration data instead of using the template trajectory. By using this method, the subject could walk on the slope and stairs continuously. Finally, %MVC of the user's EMG while walking equipped with this apparatus was measured, and the influence of the difference using between the impedance and torque control method was confirmed by interviewing the subjects. From the result, the impedance control method assisted the motion of kicking the ground, and the torque control method assisted the motion of raising-up the leg. Therefore, the impedance control method is good for gait training, and the torque control method is good for walk promotion.

This paper considers a power assist system of elbow as an example of human-assist system and describes impedance control of it. The assist system is required not only to assist the movement of elbow but also to be strictly stable. Impedance control based on position control is often used for the assist devices because the control system is simpler than that of the devices based on force control. But if the impedance parameters are made to be small in order to get good maneuverability, the system becomes unstable because of the delay of the position control system especially when the assisted tool touches high stiffness environment such as a wall. So, an impedance control method based on position control with passive elements is proposed. As a result, the stability and the effects on time delay of the proposed system showed good performance.

This paper presents an interconnection and damping assignment passivity based control (IDA-PBC) for the position and impedance control of flexible joint robot. In considering of the joint damping and with some simplification of friction, a flexible joint robot system is descripted as an port-controlled Hamiltonian system with dissipation(PCHD). Then, giving a desired Hamiltonian function which both shapes potential and kinetic energies, the control laws of position control and impedance control is derived by the algebraic IDA-PBC method, which preserves the PCHD structure of the close-loop system. Comparing with the traditional passivity based control (PBC), the proposed method gives a new explanation of the control of flexible joint robot by introducing the self-damping and cross-damping terms, which make the gain selecting procedure more intuitive and comfortable. Simulation and experiments are done to verify the proposed controller, and the results shows a promising performance both in position and impedance control.

In this paper, model-based precision force and position control of an ionic polymer metal composite (IPMC) is presented. A 23.8 mm × 3.4 mm × 0.16 mm IPMC strip was used as an actuator in a cantilever configuration. Open-loop force and position responses of an IPMC are not repeatable, and hence closed-loop precision control is of critical importance to ensure proper functioning, repeat-ability and reliability. After feedback controllers were designed and implemented with empirically obtained fourth-order plant transfer functions, the overshoot decreased from 460 to 2.8 per cent and the settling time was reduced from 37.5 to 3.22 s in force control. In position control the overshoot decreased from 333 to 20.3 per cent and the settling time was reduced from 21.5 to 2.56 s. Microscale precision force and position control capabilities of the IPMC actuator were also demonstrated experimentally. An 8 μN force resolution was achieved with a force noise of 0.5μN r.m.s., and the position resolution was 6 μm with a position noise of 2.5 μm r.m.s. The maximum force and tip displacement achieved with the IPMC actuator under closed-loop control were 2 mN and 5 mm respectively. The IPMC actuator could follow various commanded force and position trajectories such as sinusoidal and trapezoidal position profiles, and a velocity profile with a 3 mm/s maximum velocity. A novel hybrid force and position control strategy demonstrated its utility in practical micromanipulalion applications where the actuator force must be limited to prevent damaging micro-objects. High-precision control of the IPMC at low force level proved its potential for micromanufacturing and micromanipulation applications such as robotic and biomedical microgrippers.

On-line learning of robot arm impedance using neural networks

Human assist devices are expected to be developed in the field of welfare, home, factory and so on. The devices are required to not only to assist the human but also to be strictly stable. Impedance control based on position control is often used for the human assist devices because the control system is simpler than that of the devices based on force control. But if the impedance parameters are made to be smaller in order to get good maneuverability, the system becomes unstable because of the delay of the position control system especially when the assisted tools touch high stiffness environment such as a wall. In this paper, we propose an impedance control method based on position control by employing passive elements such as a mass, a spring and a damper. Then we show in a simulation that the system controlled by the proposed method with very low impedance parameters is stable even if the system touches a high stiffness environment.

Capacitive impedance control enables a power converter to mimic the voltage-current characteristics of a physical passive capacitor actively; however, existing impedance control methods cannot achieve accurate capacitive control due to parameter errors. This digest proposes a capacitive impedance control method with adaptive parameter capability, which is adaptive to changes in the parameters to maintain the capacitance of the active capacitor to the given reference with high precision. A capacitor bank volume-optimized design procedure of the active capacitor in high-power applications considering reliability design constraints is proposed as well. A 16kVA case study demonstrates the control method and design results.

Physiotherapy is the treatment to recover a patient’s mobility and limb function after an injury, illness, or disability. Rehabilitation robots can be used to replace human physiotherapists. To ensure safety during robot physical therapy, the patient’s limb needs to be controlled to track a desired joint trajectory, and the torque due to interaction force/torque needs to be measured and regulated. Therefore, hybrid impedance and admittance with position control (HIPC) is required to track the trajectory and simultaneously regulate the contact torque. The literature describes two structures of HIPC: (1) a switched framework between admittance and impedance control operating in parallel (HIPCSW); and (2) a series connection between admittance and impedance control without switching. In this study, a hybrid adaptive impedance and position-based admittance control (HAIPC) in series is developed, which consists of a proportional derivative-based admittance position controller with gravitational torque compensation and an adaptive impedance controller. An extended state observer is used to estimate the interaction joint torque due to human stiff contact with the exoskeleton without the use of force/torque sensor, which is then used in the adaptive algorithm to update the stiffness and damping gains of the adaptive impedance controller. Simulation results obtained using MATLAB show that the proposed HAIPC significantly reduces the mean absolute values of the actuation torques (control inputs) required for the shoulder and elbow joints in comparison with HIPC and HIPCSW.

Position control was applied to industrial robots when they carry out tasks such as handling, stacking, welding. However, carrying out complex tasks like grinding, polishing and deburring requires more. In these cases, the contact force, between the manipulator's end effector and the working environment, also needs to be controlled to achieve compliance. The surface tracking based on force control is the key technology for industrial robots to perform tasks like grinding, polishing. Force control requires robots to sense the information of the external environment. In this paper, a Six-Axis Force/Torque Transducer is used to acquire the contact force between the tool and the surface. Then we use the constant contact force control algorithm, together with the orientation adjustment strategy, to keep the contact force constant and ensure the tool vertical to the contact surface to realize the surface tracking. Experiments show that the scheme is efficient, and has a certain guiding significance for manipulator in industrial production tasks where force control is required.

This paper proposes an intelligent massage control system by using multi-fingered robot hand with hybrid impedance control, which is able to create the movement and the force of robot such as the human's massage. Therefore, the various massage points, such as the change of the stiffness of human skin muscle, can be controlled by using impedance control method. The hybrid impedance control is comprised of the two methods of the position-based and the force-based impedance control were applied. The position-based impedance control is used to control the lateral position of massage on the human skin muscle. On the other hand, the force-based impedance control is used to control the force of the vertical direction on human skin muscle. This paper also gives the identification of human skin muscle through robot perception of impedance to decide the parameter of impedance controller. The control strategy using impedance control to implement an adaptive control system is presented, when human condition is changed with soft and hard skin muscle. Effectiveness of massage control system by using multi- fingered robot hand with hybrid impedance control is demonstrator through actual massage experiments of pushing and rubbing motion.

Modelling and Control of an Elastic Robot Arm with Rotary and Prismatic Joints