Paralel mekanizmalar kapalı çevrim yapılardır. Paralel mekanizmalarda hareketli platform, sabit platforma en az iki noktada birbirinden bağımsız kinematik bağlantı elemanlarıyla bağlıdır. Paralel mekanizmaların avantajları yüksek katılık, hassasiyet, doğruluk, yük taşıma kapasitesi ve yüksek hız uygulamalarında çalışabilme olarak sıralanabilir. Fakat çalışma uzayları seri mekanizmalara göre daha küçüktür. Stewart Platform Mekanizması(SPM), ilk olarak 1965 yılında D. Stewart tarafından uçuş simülatörü olarak önerilen en meşhur paralel manipülatördür. Bu çalışmada iki farklı tip olan 6-3, özel yapı 6-3 SPM ve 6-4 SPM kullanılmıştır. 6-3 SPM’sı sabit ve hareketli platformdan oluşmaktadır. 6 adet lineer eyleyici sabit platforma 6 noktadan üniversal mafsallarla ve üst platforma 3 noktadan küresel mafsallarla bağlanmıştır. Ardışık lineer eyleyiciler ikili grup halinde birbirine bağlanarak üst platforma üç noktadan bağlanmışlardır. Aynı zamanda 6-4 SPM’de sabit ve hareketli platformdan oluşmaktadır. 6 adet lineer eyleyici sabit platforma 6 noktadan üniversal mafsallarla ve üst platforma 4 noktadan küresel mafsallarla bağlanmıştır. Çalışma uzayı analizine örnek olarak, 6-3 SPM, özel yapı 6-3 SPM ve 6-4 SPM’lerin ters kinematik analizleri yapılmıştır. Bu denklemler Matematica ve Matlab programları kullanılarak çözülmüştür. 6-3 SPM, özel yapı 6-3 SPM ve 6-4 SPM’lerin yönelme çalışma uzayı analizleri Euler açıları temeline dayanan ayrıklaştırma metodu kullanılarak yapılmıştır. Elde edilen sonuçlar, yorumlama açısından kolay olması için, silindirik koordinatlara dönüştürülerek yönelme çalışma uzayı grafikleri çizdirilmiştir. 6-3 SPM, özel yapı 6-3 SPM ve 6-4 SPM’lerin yönelme çalışma uzayları karşılaştırılmıştır. Aynı zamanda hareketli platformun alanı değiştirilerek 6-3 ve 6-4 SPM’lerin çalışma uzayları karşılaştırılmıştır.

Parallel mechanisms, which are closed loop mechanisms, consist of a base platform, a moving platform, and at least two links actuated in parallel. The Stewart Platform Mechanism (SPM), which is originally proposed by D. Stewart as a flight simulator in 1965, is the most renowned parallel manipulator. In 1949, the first working parallel mechanism was designed by Gough. For this reason, such a parallel mechanism is sometimes referred to as the Gough- Stewart Platform. Hunt suggested using parallel manipulators in robotic applications due to their advantages. Recent advances in high-precision technology necessitated the replacement of serial mechanisms by parallel working mechanisms in many industrial applications. The advantages of parallel manipulators are high rigidity, precision, accuracy, load carrying capacity, stiffness, ability to be utilized in high speed applications and ease of control are given in literature by many authors. However, the workspace of parallel mechanism is smaller than serial mechanism. In addition to this, a number of studies on parallel mechanisms, often on the 3 degrees of freedom (DOF) and 6 DOF types exist in open literature. 6-3 SPM, studied in this thesis, consists of a fixed base platform and a mobile platform. Six linear actuators are connected to the base at six points via universal joints and to the top platform at three points via spherical joints. Consecutive linear actuators are attached to each other in groups of two so that there are three points of attachment to the top platform. The particular 6-3 SPM’s moving platform is connected to spherical joints via small rods. 6-4 SPM also consists of a base platform and a mobile platform. Six linear actuators are connected to the base at six points via universal joints and to the top platform at four points via spherical joints. These structures are called 6-UPS (Universal-Prismatic- Spherical) mechanisms due to the types of joints in the architecture. Both platforms have 6 DOF, ability to move positional and orientation in 3 directions. To give a model for the workspace analysis of 6-3 SPM, the particular 6-3 SPM and 6-4 Stewart platform mechanisms kinematics are carried out. Workspace analysis of parallel mechanisms is not generalized so far in literature. However, many problems, like small workspace, poor dexterity and difficulty in design are still open for an efficient exploitation of the concept. Most of the studies in the literature examined two dimensional orientation workspace. Some other studies cover only the boundary scanned 3D orientation workspace. In literature, workspace analysis methods are classified into 3 main groups as the discretization method, geometrical method and the Jacobian matrix technique. After carrying out kinematic analysis, discretization method, which is based on Euler angles, is used to represent the orientation workspace of 6-3 SPM, the particular 6-3 SPM and 6-4 SPM. In order to simplify interpretation, the orientation workspace is illustrated in a cylindrical coordinate system. The orientation workspaces of the 6-3 SPM, the particular 6-3 SPM, and the 6-4 SPM are compared. In this study, the method used is fully scanned orientation workspace, which is extended, in the mostly workable direction for 6-3 SPM, the particular 6-3 SPM and 6-4 SPM. Possible gaps, which are omitted in representation of boundary orientation workspace, can be realized in fully scanned orientation workspace. For these types of working mechanisms, i.e. a mechanical tool used material processing the determination of the points, which makes the workspace maximum be outlined. The workspace of the 6-4 mechanism with trapezoidal upper platform is larger than that of the 6-3 mechanisms with triangular upper platform. However, in the case of the 6-4 mechanism, there are greater gaps within the workspace. Even though the workspace of the 6-4 mechanism is greater than that of the 6-3 mechanism, the trapezoid platform cannot reach every point in the vicinity of C, gravity centre, and at the boundaries of the workspace. A 6-3 SPM should be preferred if it is desired to work close to C and the boundaries of the workspace as in flight simulator case. In addition, a triangular moving platform is structurally more stable than a trapezoidal moving platform. When greater or distributed loads need to be carried by the mechanism, such as in the case of heavy loads lifting, a trapezoidal moving platform should be preferred.