Ovidiu Antonescu

Modeling and Simulation of the Specific Mechanisms Used in Convertible Automobiles

The paper deals with linkages used to actuate the retractable top of convertible passenger car, which are either a simple articulated 4-bar mechanism or a stacking multi-contour n-bar mechanism. The car top that can fold or unfold is consisting of two or three hard components or flexible material as textile. In the case of flexible top, the folding space is smaller, occupying only a relative small volume of the trunk. The folding linkage of the hard top is a planar kinematic chain with articulated bars which allows the two or three top parts to be stacked into the trunk room. To be observed that the first hard component of the kinematic chain is the car rear screen and the second hard part is actually the retractable top. In order to fold the car top and the rear screen, the door trunk is actuated by means of a simple hinge pair or a 4-bar mechanism. In the case of a larger passenger car, the top consists of two parts and together with the rear screen form the open kinematic chain which can be closed by means of some stacked kinematic chains. Using CAD modeling and kinematic simulation of the retractable textile car top linkage used on convertibles, the mechanism efficiency regarding its operation can be improved. Through Inventor® software the user can modify any part or subassembly of the mechanism at any moment. This can be done by means of the parametric design which allows that any changing on a component to be instantaneous reflected on the assembly which that part belongs to.

Geometric Synthesis of the Actuating Mechanisms of Urban Bus Doors

The paper presents the method of geometrical synthesis of two new kinematic schemes of articulated planar mechanisms used to actuate the urban bus doors. The stages of solving geometrical synthesis for the two and three relative-associated positions of the bars articulated to the body are performed. In order to optimize the geometric synthesis and to avoid the mechanism stalling, the limiting of the pressure angle is required. One of the two proposed mechanisms has kinematic chains of dyad type in its structure, and the other mechanism also includes a triad-type kinematic chain. The new solutions have a smaller swept volume regarding the control mechanism.

Topological Structure of the Actuating Mechanisms of the Urban Buses Doors

The paper analyzes the structural and geometric-kinematic aspects of the articulated bar mechanisms used to actuate the doors of urban buses. A mechanism of this kind consists of two main parts: the control mechanism mounted under or above the door, and the crank-slider final mechanism which actuates the folding doors. The analyzed mechanisms have in their structure simple dyad chains or complex chains of triad type. For these types of planar linkages that are equipping the urban buses, the topological and geometric structure is analyzed in order to find solutions to minimize the swept volume of them.

Research on some auxiliary mechanisms used in passenger cars

There are complex mechanisms used as auxiliary systems on passenger cars as following: opening/closing door mechanisms, winding window mechanisms, windshield / rear screen wiper mechanisms, lifting/lowering hood / trunk door mechanisms, canopy car mechanisms. The paper presents the research results regarding the topological structure and geometric analysis of the planar linkages that are used to actuate passenger car doors. There are three types of passenger car door movements: rotation, sliding and planar rotational-sliding. Usually, the passenger cars are equipped with rotate doors on which the motion of rotation is limited and it occurs in horizontal plane. The sliding doors are designated, usually, for the back passengers of the car. Unlike the rotate doors, the sliding ones are using a minimum side swept volume which is a major advantage, especially, on parking. The paper highlights some mechanisms with bars and gears that are used instead of the classic hinges. The planar quadrilateral mechanism can replace the hinge for opening/closing the door which is rigid connected with the coupler of the linkage. Also, the planar quadrilateral mechanism is used for lifting/lowering the canopy car roof which is rigid connected with the “doors” and the windshield. If the mechanism is an articulated parallelogram, the assembly of the doors+roof+windshield performs a circular sliding motion. Note that the quadrilateral (parallelogram) mechanism is double, with the two rockers working together and the coupler being a single part (doors + roof + windshield). The planar articulated bi-contour mechanism is type Watt being used to actuate the passenger car door, replacing the classic hinge. This Watt mechanism is obtained through the amplification of a quadrilateral mechanism (mono-contour) with a kinematic articulated chain type dyad RRR. The door is rigid connected with one bar of the dyad chain, which allows a planar rotational-sliding motion in horizontal plane. This design allows the door, in the open position, to occupy an “offset” position with respect to the car body. In order to increase the access comfort into the car, the recent researches focus on using pneumatic actuators for driving the car doors.

Synthesis of the Mechanisms Used for Reverse Driving on Continuously Variable Transmissions (CVT)

The paper presents two kinematic schemes of the reverse driving mechanism on CVT’s, the first one for rear-wheel drive, and the second one for front-wheel drive. For the first kinematic scheme, the reverse driving mechanism consists of a planetary cylindrical gear set and a multi-disk brake. In order to achieve a better efficiency for reverse driving, the authors propose a new kinematic structure of a planetary cylindrical gear mechanism, simpler than the existing designs. While describing a synthesis of the new kinematic solution, special attention was granted to maintaining the advantages of each of the two existing mechanisms, and highlighting the advantage of using less cylindrical gears.

Metal Pushing V-Belt Continuously Variable Transmissions (CVT) Used in Motor Vehicles

The paper presents 3D modeling of a trapezoidal element (V-element) of a metal pushing V-belt. This type of belt is used on the Continuously Variable Transmissions (CVT) with friction pulleys that equip low and medium capacity motor vehicles. Also, the structural analysis of the V-belt element with regards to the material strength is presented. Modeling and simulation have been accomplished by an advanced CAD – CAM – CAE software which permits three-dimensional virtual design of the V-element or the entire belt.

Review on Mechanisms Used as Handbrake in Carriages and Locomotives

The paper presents some kinematic schemes of the major mechanisms used as linkages for handbrakes on railway carriages and locomotives. For the classical linkage with brake shoes on the axle wheels of carriages or locomotives, articulated mechanisms with bars, gears, articulated chains and motion bolts are used. In the case of linkage with planar brake pads, the disk brake consists of deformable elements, such as cables. At two-axle or four-axle carriages (bogies with two axles) with central brake linkage, there is only one mechanism for the handbrake. Diesel-electric locomotives with three-axle bogies have two brake mechanisms for each bogie.

Compounding of Concurential Rotation Movements

By the composing of the rotation movements with the concurrent instantaneous axes in a point, a rotation movement with the instantaneous axis passing through that point is obtained. The resultant instantaneous angular velocity is sum of the component angular velocity. As examples of the mechanical systems in which appear the concurrent rotation movements are: the pivot bearings of the radial-axial with balls type, the ball radial bearings and the planetary mechanisms with bevel gears which are used both as differential to automotives and as orientation mechanisms (wrist) on the industrial robots.

Front Stop Lamps for a Safer Traffic

Engineering Objective: The paper deals with an innovative idea of placing the stop lamps not only in the rear of the vehicle as usual but in the front of it too. By doing this the traffic safety would increase significantly since everyone involved on it would know that the driver is stopping the vehicle. Especially the pedestrians would benefit of these front brake lights when they are crossing the street. The stop lamps may be placed near to the headlights but they would be difficult to be observed during the night. Thus, a better solution is placing them separately as some turn signals. What does the paper offer that is new in the field in comparison to other works of the author: The paper offers an idea completely new in the automotive filed and it is also new comparing to other works of the author. Conclusion: The innovative idea of placing the stop lamps in the front of the vehicle would offer a safer traffic not only for pedestrians but also for all involved in the traffic.

Mobility and Direct Kinematics of Parallel Manipulators RSS Type - 3 Actuators

The parallel manipulators are multi-mobile planar or spatial mechanisms with two to six kinematical chains that connect two rigid bodies, generically named platforms. The parallel manipulator is a complex topological structure, having the joints of various types. The most frequently utilized joints are: the mono-mobile kinematical pairs (revolute R or prismatic), the bi-mobile cylindrical pairs C and the tri-mobile spherical pairs S. One of the most important problems in parallel manipulators kinematics is finding the solution of direct kinematics. The paper presents a new way for the calculation of mobility and a new method for the direct kinematics of parallel manipulators RSS type, which are driven by three actuators.