图 上海文通大￥ -b口 HAa JLAO TONr:UNpT LECTURE 5 ME371/ME337 DESIGN AND MANUFACTURING Graphical Linkage Synthesis Covered: Ch3-in Design of Machinery SHA 国 上海文通大学 OUTLINE ▣Kinematic Synthesis Dimensional Synthesis Quick-Return Mechanisms 1
1 Graphical Linkage Synthesis LECTURE 5 ME371/ME337 DESIGN AND MANUFACTURING Covered：Ch3- in Design of Machinery OUTLINE Kinematic Synthesis Dimensional Synthesis Quick-Return Mechanisms
国上泽发大半 Analysis OR Synthesis HAa ILAO ToNr:UNpi Analysis or Synthesis-A generic view (Uni-directional iterative Y2 among multiple points) Synthesis Analysis Synthesis Analysis X3 The Design Space The Performance Space (Sets of design parameters X (Sets of performance parameters Y and their specification ranges) and their requirement ranges) Most engineering design practice involves a combination of synthesis and analysis Kinematics:the study of the motion of mechanisms and methods of creating them. 国 上潘久大学 Kinematic Analysis Given a certain mechanism,the motion characteristics of its components will be determined by Kinematic Analysis. Task of analysis contains all principal dimensions of the mechanism,interconnections of its links,and the specification of the input motion or method of actuation. The objective is to find the displacements,velocities, accelerations,shock or jerk,as well as the paths described and motions performed by certain elements. T=Fn拼 Tout=Fout rout v->0 rock 2
2 Analysis or Synthesis-A generic view Y3 X2 X1 X3 Y2 Y1 The Design Space (Sets of design parameters X and their specification ranges) The Performance Space (Sets of performance parameters Y and their requirement ranges) Synthesis Analysis Synthesis Analysis (Uni-directional iterative among multiple points) Analysis OR Synthesis Most engineering design practice involves a combination of synthesis and analysis Kinematics : the study of the motion of mechanisms and methods of creating them. Kinematic Analysis Given a certain mechanism, the motion characteristics of its components will be determined by Kinematic Analysis. Task of analysis contains all principal dimensions of the mechanism, interconnections of its links, and the specification of the input motion or method of actuation. The objective is to find the displacements, velocities, accelerations, shock or jerk, as well as the paths described and motions performed by certain elements
图 上海文通大￥ Kinematic Synthesis HA ILAO ToNr:UNpin 国 Synthesis:the creation of potential solutions in the absence of a well defined algorithm which configures or predict the solution. The essence of Kinematic Synthesis is that the motion is given and the mechanism is to be found. The areas of synthesis may be grouped into two categories:type synthesis and dimensional synthesis. >Type synthesis:the definition of the proper type of mechanism best suited to the problem >Dimensional synthesis:the determination of the proportions (lengths)of the links necessary to accomplish the desired motions 国 上海文通大学 Kinematic Synthesis Design a mechanism to satisfy particular motion requirements. Functional relationship between input and output(linear to linear.linear to rotational.rotational to linear.rotational to rotational)(Function Generation) Follow a particular path(Path Generation) Be of a certain orientation at particular points(Motion Generation) Other considerations?: ·Full crank rotation ·Space Constraints ·Transmission Angle Mechanical Advantage 3
3 Kinematic Synthesis Synthesis: the creation of potential solutions in the absence of a well defined algorithm which configures or predict the solution. The essence of Kinematic Synthesis is that the motion is given and the mechanism is to be found. The areas of synthesis may be grouped into two categories: type synthesis and dimensional synthesis. Type synthesis: the definition of the proper type of mechanism best suited to the problem Dimensional synthesis: the determination of the proportions (lengths) of the links necessary to accomplish the desired motions Design a mechanism to satisfy particular motion requirements. • Functional relationship between input and output (linear to linear, linear to rotational, rotational to linear, rotational to rotational) (Function Generation) • Follow a particular path (Path Generation) • Be of a certain orientation at particular points (Motion Generation) Other considerations?: • Full crank rotation • Space Constraints • Transmission Angle • Mechanical Advantage Kinematic Synthesis
图上泽充大学 Task of kinematic synthesis GN如T94 Darte 4-Dar linkage Clozaifiostion 品D D Belt2 Most important step is to clarify the performance Path tenerate requirements with motions. The motions can be modeled graphically or analytically. 位 国 上潘久大学 OUTLINE ▣Kinematic Synthesis Dimensional Synthesis Quick-Return Mechanisms 4
4 Task of kinematic synthesis Most important step is to clarify the performance requirements with motions. The motions can be modeled graphically or analytically. Ⅰ Ⅱ D OUTLINE Kinematic Synthesis Dimensional Synthesis Quick-Return Mechanisms
图 上泽文通大学 Type synthesis TYPE SYNTHESIS:the definition of the proper type of mechanism best suited to the problem. 国 Example:Design a device to track the straight-line motion of a part on a conveyor belt and spray it with a chemical coating as it passes by. -High,constant speed; -A straight-line linkage -Good accuracy and repeatability -A cam and follower -reliable -An air cylinder -A hydraulic cylinder -A robot -A solenoid 国 上海文通大学 Dimensional synthesis Dimensional synthesis the determination of the proportions (lengths)of the links necessary to accomplish the desired motions. Through type synthesis,you have determined that a linkage is the most appropriate solution to the problem. The simplest and quickest methods are graphical.This is up to three design positions 5
5 TYPE SYNTHESIS : the definition of the proper type of mechanism best suited to the problem. Example: Design a device to track the straight-line motion of a part on a conveyor belt and spray it with a chemical coating as it passes by. Type synthesis Trade-off - High, constant speed; - Good accuracy and repeatability - reliable - A straight-line linkage - A cam and follower - An air cylinder - A hydraulic cylinder - A robot - A solenoid Dimensional synthesis : the determination of the proportions (lengths) of the links necessary to accomplish the desired motions. Through type synthesis, you have determined that a linkage is the most appropriate solution to the problem. The simplest and quickest methods are graphical. This is up to three design positions Dimensional synthesis
图 上海文通大￥ Dimensional synthesis Aa ILAO ToNr:UNpain Euclidean geometry(欧几里得几何) The rules for bisection of lines and angles,properties of parallel and perpendicular lines,and definitions of arcs. Compass,protractor,and rule are the only tools needed for graphical linkage synthesis 国 上久通大学 Two-Position synthesis Rocker output(pure rotation)and coupler output (complex motion) Rocker output is most suitable for situations in which a Grashof crank-rocker is desired.A case of function generation. Coupler output is more general and is a simple case of motion generation in which This solution will frequently lead to a triple-rocker. The fourbar triple-rocker can be motor driven by the addition of a dyad(twobar chain),which makes the final result a Watt's sixbar containing a Grashof fourbar subchain. 6
6 Euclidean geometry (欧几里得几何) The rules for bisection of lines and angles, properties of parallel and perpendicular lines, and definitions of arcs. Compass, protractor, and rule are the only tools needed for graphical linkage synthesis Dimensional synthesis Rocker output (pure rotation) and coupler output (complex motion) Rocker output is most suitable for situations in which a Grashof crank-rocker is desired. A case of function generation. Coupler output is more general and is a simple case of motion generation in which This solution will frequently lead to a triple-rocker. The fourbar triple-rocker can be motor driven by the addition of a dyad (twobar chain), which makes the final result a Watt's sixbar containing a Grashof fourbar subchain. Two – Position synthesis
圈上泽充大学 1.Two-Position synthesis GHA ILAO TONE:UNpin Problem:Design a fourbar Grashof crank-rocker to give 45 of rocker rotation with equal time forward and back,from a constant speed motor input. Draw O,B in two extreme Link 3 positions Draw chord B,B2 in either Link 2 direction Select point O2 Bisect B,B,and draw circle of that radius at O, Crank-O2A,Coupler AB, Rocker O2B,Ground O2O 02 64 0 Your choice 国 上久通大学 Two-Position synthesis 1.Grashoff non-quick return crank-rocker (b)Finished llnkage Link 3 Link 2 B> A 0 Link 4 Link I Link 3 7
7 1. Two – Position synthesis • Draw O4B in two extreme positions • Draw chord B1B2 in either direction • Select point O2 • Bisect B1B2 and draw circle of that radius at O2 • Crank-O2A, Coupler AB, Rocker O4B, Ground O2O4 45° Problem: Design a fourbar Grashof crank-rocker to give 45°of rocker rotation with equal time forward and back, from a constant speed motor input. 1. Grashoff non-quick return crank-rocker Two – Position synthesis
国上海夫大￥ Two-Position synthesis Problem:Design a fourbar linkage to move link CD from position CD to C2D2 Construct perpendicular bisectors C,C2 and D,D2 Intersection of the bisectors is the rotopole(the ground location旋转极心) The output link is shown in its two positions Link 4 0 Rotopole 15 国 上海文通大学 A TONG UNTVT Two -Position synthesis 2.Link thru 2 positions as rocker You can add a dyad by picking point B on the output link Link4 D1 Link 2 C D Link 3 02 Link 1 Rotopole 8
8 15 Construct perpendicular bisectors C1C2 and D1D2 Intersection of the bisectors is the rotopole (the ground location 旋转极心) The output link is shown in its two positions Problem: Design a fourbar linkage to move link CD from position C1D1 to C2D2 Two – Position synthesis 16 You can add a dyad by picking point B on the output link 2. Link thru 2 positions as rocker Two – Position synthesis
国上海夫大￥ Two-Position synthesis Problem:Design a fourbar linkage to move the link CD shown from position C,D,to C2D2(with moving pivots at C and D) D Link 4 Construct bisectors of C,C2 Link 3 and D1D2 Any point of bisector of C1C2 can be O2 and any point on bisector of DiD2 can be O4 Links are O2C1.C1D1.D104. and ground O204 Link 2 国 上潘久大学 Two-Position synthesis M NAO TOND Problem:Design a dyad to control and limit the extremes of motion of the linkage in late example to its two design positions The dyad does not have to be along the O2C1 line.This allows a choice of D many places for Os C Link 6 Link 6 0 B: 0 9
9 Construct bisectors of C1C2 and D1D2. Any point of bisector of C1C2 can be O2 and any point on bisector of D1D2 can be O4 Links are O2C1, C1D1, D1O4, and ground O2O4 Pick Pick Problem: Design a fourbar linkage to move the link CD shown from position C1D1 to C2D2 (with moving pivots at C and D) Two – Position synthesis The dyad does not have to be along the O2C1 line. This allows a choice of many places for O6 B1 B1 Problem: Design a dyad to control and limit the extremes of motion of the linkage in late example to its two design positions Two – Position synthesis
图 上泽文通大学 Three-Position synthesis HA ILAO TONn UNnin Allows the definition of three positions of a line in the plane Create a fourbar linkage configuration to move it to each of those three positions. The synthesis technique is a logical extension of the method used for two-position synthesis with coupler output. Require the addition of a dyad to control and limit its motion to the positions of interest. 上久通大学 Three-Position synthesis Link thru 3 positions as coupler A, A B B盼 B3 Ao 10
10 Three– Position synthesis Allows the definition of three positions of a line in the plane Create a fourbar linkage configuration to move it to each of those three positions. The synthesis technique is a logical extension of the method used for two-position synthesis with coupler output. Require the addition of a dyad to control and limit its motion to the positions of interest. A0 B0 A1 B1 A2 B2 A3 B3 Link thru 3 positions as coupler Three– Position synthesis
