Research On Friction Characteristics And Dynamic Behavior Of The Feed System Of Sliding Joint Surface

The sliding joint surface feed system is an important part of the heavy-duty precision CNC machine tool.Affected by the sudden change of driving acceleration and the friction of the joint surface,the vibration phenomenon of the sliding table along the feed direction is not only affected by the change of the movement state such as the start-stop commutation.The machining quality of the parts also causes adverse effects such as tool chipping and loosening of machine tool fixtures.In order to study the factors that affect the movement accuracy of the sliding table,this paper takes the sliding joint surface feed system as the research object,establishes the joint surface dynamic friction model,and analyzes the non-linear characteristics of friction and the influence of the motor drive mode on the dynamic behavior of the sliding table.First of all,the friction static and dynamic characteristics are experimentally studied by the UMT-TriboLab friction and wear testing machine,and it is obtained that the friction dynamic characteristics are essentially inertial characteristics,which are related to the acceleration of the relative motion of the joint surface.In order to describe the characteristics of the friction force continuously experienced from zero through the maximum static friction to dynamic friction during the startup stage of the feed system,the friction state is simulated by combining the elastic deformation of the contact bristles between the surfaces in the LuGre model,and the six static and dynamic parameters of the LuGre model are identified by the particle swarm algorithm.The friction dynamics model of the sliding joint surface is established in Simulink.It is found that when a step force smaller than the static friction force is applied to the joint surface tangentially,the joint surface bristles are equivalent to a massless spring damping system.When the joint surface bristles are excited by the step force Hair deformation and friction will cause oscillation convergence phenomenon and cause tangential vibration of the sliding table.In order to analyze the influence of the friction of the joint surface on the dynamic behavior of the sliding feed system,a concentrated mass model of the feed system was established,and the Simulink-ADAMS friction dynamics co-simulation study was carried out.The damping characteristics of the friction pre-slip phase were obtained to reduce the sliding table vibration during the starting phase Phenomenon,the negative damping characteristic of friction Stribeck exacerbates the vibration phenomenon in the starting stage of the slide.In addition,it is analyzed that the inertial force excitation generated by the motor driving jerk is one of the reasons that cause the sliding table to vibrate along the feed direction.When the motor is driven by an S-shaped speed curve with a small amplitude of the driving acceleration frequency domain,the curve is the sliding table generates a small inertial force excitation,so the vibration phenomenon in the feeding direction of the sliding table is also smaller than the trapezoidal curve.Aiming at the problem that the S-shaped speed curve is affected by several motion parameter constraints,this paper proposes a motor speed curve planning method based on the principle that any motion state time interval during the target motion process is always greater than or equal to zero.Aiming at the sliding j oint surface feed system,experimental verification and simulation put forward a method to reduce the vibration of the sliding table along the feed direction at the start stage by using a speed curve with a lower amplitude of the driving acceleration in the frequency domain.At the same time,experiments found that when the motor is driven by a third-order S-shaped speed curve,the tracking error during the movement of the sliding table is smaller than the trapezoidal speed curve.Aiming at the problem that the tracking error of the sliding table obtained in the experiment does not show the problem related to the driving acceleration,the feed system motor control model is established,and the simulation shows the same positive correlation law of the sliding table tracking error and the driving speed as the experiment.Error is one of the reasons that affect the accuracy of the feed system.Aiming at the sliding joint surface feed system,this paper analyzes the influence of joint surface friction,motor drive parameters and speed curve on the dynamic behavior of the feed system through experimental simulation.The research results are for reducing the vibration and tracking of the sliding table in the feed direction.Error,there is a certain reference value in improving the motion accuracy and stability of the sliding feed system.