Modeling of controlled motion of semi-passively actuated SCARA-like robot

The controlled motion of a new structure of manipulator robot is under study. In comparison with the well-known SCARA robot the proposed robotic system has the following new features: in addition to powered drives it comprisesseveral unpowered (passive) spring-damper-like drives. An additional link has also been incorporated into the structure that gives the possibility to obtain a semipassively actuated closed-loop chain robot. Special emphasis is put on a study of the interaction between the controlling stimuli of the powered drives and the torquesexerted by the unpowered drives needed to provide the energy-optimal motion of the robot. Computer simulations have demonstrated the numerical efficiency of thedeveloped algorithms and have proved several advantages of the considered semipassively actuated closed-loop robot

Modeling of controlled motion of semi-passively actuated SCARA-like robot

The controlled motion of a new structure of manipulator robot is under study. In comparison with the well-known SCARA robot the proposed robotic system has the following new features: in addition to powered drives it comprisesseveral unpowered (passive) spring-damper-like drives. An additional link has also been incorporated into the structure that gives the possibility to obtain a semipassively actuated closed-loop chain robot. Special emphasis is put on a study of the interaction between the controlling stimuli of the powered drives and the torquesexerted by the unpowered drives needed to provide the energy-optimal motion of the robot. Computer simulations have demonstrated the numerical efficiency of thedeveloped algorithms and have proved several advantages of the considered semipassively actuated closed-loop robot

Optimisation of controlled motion of closed-loop chain manipulator robots with different degree and type of actuation

A number of energy-optimal control problems for a new structure of closed-loop manipulator robot are considered. We present methodology and algorithm that is suitable for solving optimization problems for manipulator robots with different degree and type of actuation. This methodology isbased on polynomial and Fourier series approximation of independently varying functions and conversion of the initial optimal control problem into the constrained parameter optimization problem. The methodology has been successfully used for optimization of under-, fully-, and overactuated robots having both external (powered) drives and internal (unpowered or passive) spring-damper-like drives. Comparison analysis of the simulation results of the obtained energy-optimal control processes fordifferent manipulator robots is presented

Regenerative braking for an electric vehicle with a high-speed drive at the front axle

The main contribution of this paper lies in the development of a novel front-to-rear axle brake force distribution strategy for the regenerative braking control of a vehicle with a high-speed electric drive unit at the front axle. The strategy adapts the brake proportioning to provide extended room for energy recuperation of the electric motor when the vehicle drivability and safety requirements permit. In detail, the strategy is adaptive to cornering intensity enabling the range to be further extended in real-world applications. The regenerative braking control features a brake blending control algorithm and a powertrain controller, which are decisive for enhancing the braking performance. Lastly, the regenerative braking control is implemented in the highfidelity simulation environment Simcenter Amesim, where system efficiency and regenerative brake performance are analysed. Results confirm that the designed regenerative braking greatly improves the effectiveness of energy recuperation for a front-wheel driven electric vehicle with a high-speed drive at the front axle. In conclusion, it is shown that it is feasible to use the high-speed drive with the proposed control design for regenerative braking

Experimental verification of understeer compensation by four wheel braking

This study is designed to validate a new approach to understeer mitigation chassis control, based on a particlemotion reference: parabolic path reference (PPR). Considering the scenario of excess entry speed into a curve,related to run-off-road crashes, the aim is that automatic braking minimizes lateral deviation from the target pathby using an optimal combination of deceleration, cornering forces and yaw moments. Previous simulationstudies showed that four-wheel braking can achieve this much better than a conventional form of yaw momentcontrol (DYC). The aim of this work is to verify this on a test track with an experimental vehicle, and to compareperformance with DYC and an uncontrolled vehicle. Experiments were performed with a front-wheel-drivepassenger vehicle equipped with an additional four identical brake callipers controlled via an electro-hydraulicbrake (EHB) system, enabling individual brake control. Minimizing the maximum deviation from the intendedcurve radius is the control objective. Feedback to the controller consists of the available steering wheel angle,wheel speeds, yaw rate and lateral acceleration sensors in the vehicle. Additional to these variables, also thevehicle position was logged using a GPS system. It was found that PPR is superior to DYC in reducing themaximum deviation from the intended path, confirming the trends previously found in simulations. Furthermore,the PPR concept is found to be inherently more stable than DYC since more brake force is applied to the outerwheels than the inner wheels throughout the manoeuvre. The experiments involve a first implementation of aPPR control which is not a fully closed-loop control intervention and tuned to a step steer (transition fromstraight to fixed-radius curve. This is the first study to explicitly and systematically evaluate this new approachto understeer mitigation. The approach is fundamentally different from common DYC and suggests the potentialfor a new generation of controllers based on trajectory control via chassis actuators

Design and control of model based steering feel reference in an electric power assisted steering system

Electric Power Assisted Steering (EPAS) system is a current state of the art technology for providing the steering torque support. The interaction of the steering system with the driver is principally governed by the EPAS control method. This paper proposes a control concept for designing the steering feel with a model based approach. The reference steering feel is defined in virtual dynamics for tracking. The layout of the reference model and the control architecture is discussed at first and then the decoupling of EPAS motor dynamics using a feedback control is shown. An example of how a change in steering feel reference (as desired by the driver) creates a change in steering feedback is further exhibited. The ultimate goal is to provide the driver with a tunable steering feel. For this, the verification is performed in simulation environment

Direct yaw moment control for enhancing handling quality of lightweight electric vehicles with large load-to-curb weight ratio

In this paper a vehicle dynamics control system is designed to compensate the change in vehicle handling dynamics of lightweight vehicles due to variation in loading conditions and the effectiveness of the proposed design is verified by simulations and an experimental study using a fixed-base driving simulator. Considering the electrification of future mobility, the target vehicle of this research is a lightweight vehicle equipped with in-wheel motors that can generate an additional direct yaw moment by transverse distribution of traction forces to control vehicle yawing as well as side slip motions. Previously, the change in vehicle handling dynamics for various loading conditions have been analyzed by using a linear two-wheel vehicle model in planar motion and a control law of the DYC system based on feed-forward of front steering angular velocity and feedback of vehicle yaw rate. The feed-forward controller is derived based on the model following control with approximation of the vehicle dynamics to 1st-order transfer function. To make the determination of the yaw rate feedback gain model-based and adaptable to various vehicle velocity conditions, this paper selects a method where the yaw rate feedback gain in the DYC system is determined in a way that the steady-state yaw rate gain of the controlled loaded vehicle matches the gain of the unloaded vehicle. The DYC system is simulated in a single lane change maneuver to confirm the improved responsiveness of the vehicle while simulations of a double-lane change maneuver with a driver steering model confirms the effectiveness of the DYC system to support tracking control. Finally, the effectiveness of the proposed DYC system is also verified in an experimental study with ten human drivers using a fix-based driving simulator

When will cars drive themselves?

There are many claims made about the progress of autonomousvehicles and their imminent arrival on UK roads. Professor TimGordon, Head of Engineering at the University of Lincoln, andMathias Lidberg, Associate Professor at Chalmers University ofTechnology, look behind the headline hype to see what progresshas been made and how measures already implemented haveincreased automation

Design of Optimal Control Processes for Closed-Loop Chain SCARA-Like Robots

The design of optimal control processes for closed-loop chain SCARA-like robots is the subject of this thesis. In comparison with the well-known SCARA robot, the proposed new structure is characterized by the incorporation of an additional powered actuator, several unpoweredactuators and an additional link that gives a closed-loop chain robot. The performance of the SCARA-like robot with various arrangements of powered and unpowered actuators isaddressed by formulating and solving energy-optimal and time-optimal control problems for periodic pick-and-place operations in the horizontal plane. Two computational methods suitable for solving optimal control problems for two-degree-of-freedom closed-loop chain SCARA-like robots are developed. With the direct parameter optimization approach, the relevant optimal control problems are converted into nonlinear programming problems using an inverse dynamics based method with polynomial-Fourierseries approximation of the generalized coordinates and the redundant torques. The resulting constrained nonlinear optimization problems are solved using sequential quadraticprogramming (SQP). An indirect computational method based on Pontryagins maximum principle is also developed. The necessary conditions of optimality are derived for the problems considered, and the resulting multi-point boundary-value problems are solved with a smoothing-continuation approach and an adaptive collocation method.In closed-loop chain robots with more actuators than degrees-of-freedom (overactuation), the dynamic redundancy enables optimization of the force distribution. Unpowered spring-like drives can assist the powered actuators or control some of the degrees-of-freedom of a manipulator robot (semi-passive control). Here, the advantages of overactuation and semi-passive control for the SCARA-like robots are demonstrated analytically and numerically forboth given motion and periodic pick-and-place operations.The numerical results for the solutions to the energy-optimal control problems show that the energy consumption and maximum torque required of the active actuators for typical pick-and-place operations can be reduced by using overactuation or adding unpowered drives to the structure of the robot. Using semi-passive control of the SCARA-like robot also allows simplification of the control system by reducing the number of powered actuators (underactuation). The results from the time-optimal control problems confirm the advantages of overactuation and semi-passive control.The results obtained in this thesis suggest that other mechanical systems and machines with periodic motion, such as various robots, automatic cyclic machines and bipedal robots, can benefit from overactuation and semi-passive control

Design of Optimal Control Processes for Closed-Loop Chain SCARA-Like Robots

The design of optimal control processes for closed-loop chain SCARA-like robots is the subject of this thesis. In comparison with the well-known SCARA robot, the proposed new structure is characterized by the incorporation of an additional powered actuator, several unpoweredactuators and an additional link that gives a closed-loop chain robot. The performance of the SCARA-like robot with various arrangements of powered and unpowered actuators isaddressed by formulating and solving energy-optimal and time-optimal control problems for periodic pick-and-place operations in the horizontal plane. Two computational methods suitable for solving optimal control problems for two-degree-of-freedom closed-loop chain SCARA-like robots are developed. With the direct parameter optimization approach, the relevant optimal control problems are converted into nonlinear programming problems using an inverse dynamics based method with polynomial-Fourierseries approximation of the generalized coordinates and the redundant torques. The resulting constrained nonlinear optimization problems are solved using sequential quadraticprogramming (SQP). An indirect computational method based on Pontryagins maximum principle is also developed. The necessary conditions of optimality are derived for the problems considered, and the resulting multi-point boundary-value problems are solved with a smoothing-continuation approach and an adaptive collocation method.In closed-loop chain robots with more actuators than degrees-of-freedom (overactuation), the dynamic redundancy enables optimization of the force distribution. Unpowered spring-like drives can assist the powered actuators or control some of the degrees-of-freedom of a manipulator robot (semi-passive control). Here, the advantages of overactuation and semi-passive control for the SCARA-like robots are demonstrated analytically and numerically forboth given motion and periodic pick-and-place operations.The numerical results for the solutions to the energy-optimal control problems show that the energy consumption and maximum torque required of the active actuators for typical pick-and-place operations can be reduced by using overactuation or adding unpowered drives to the structure of the robot. Using semi-passive control of the SCARA-like robot also allows simplification of the control system by reducing the number of powered actuators (underactuation). The results from the time-optimal control problems confirm the advantages of overactuation and semi-passive control.The results obtained in this thesis suggest that other mechanical systems and machines with periodic motion, such as various robots, automatic cyclic machines and bipedal robots, can benefit from overactuation and semi-passive control