A robotic device for controlling an instrument, comprising: (a) a serial kinematic chain of six rotational degrees of freedom and one translational degree of freedom, wherein the kinematic chain comprises six circular cross-roller bearings (211, 212, 213, 214, 215, 216, 410, 510), wherein in the kinematic chain each two adjacent circular cross-roller bearings (211, 212)(212, 213)(213, 214)(214, 215)(215, 216)(410, 420) are more or less perpendicularly aligned and connected to each other such that the six circular cross-roller bearings form a stacked serial kinematic chain arrangement, wherein each of the circular cross-roller bearings have an inner ring and an outer ring wherein the two adjacent circular cross-roller bearings (211, 212)(212, 213)(213, 214)(214, 215)(215, 216)(410, 420) are rigidly connected to each other through a rigid connection element allowing the two adjacent cross-roller bearings to move with respect to each other connecting the inner ring of the first circular cross-roller bearing to the outer ring of the second circular cross-roller bearing in the more or less perpendicularly alignment, and wherein the serial kinematic chain is extended by one or two linear cross-roller bearings (221, 222) adding a translation degree of freedom, wherein the one or two linear cross-roller bearings (221, 222) are connected to the inner ring of the top or last circular cross-roller bearing in the chain of six interconnected circular cross-roller bearings; and (b) an instrument mounted to the two linear cross-roller bearings, characterized in that each one of the rotational degrees of freedom can be changed by a locking element to lock the degree of freedom, wherein the locking element is configured to lock the degree of freedom of a bearing by means of locking a first rigid connection element to a second rigid connection element, where the first rigid connection element connects the inner ring of an adjacent previous bearing to the outer ring of the bearing and where the second rigid connection element is rigidly connected to the inner ring of the bearing and to the outer ring of the adjacent following bearing, and wherein the locking element is enabled or disabled by a push button. (a) a serial kinematic chain of six rotational degrees of freedom and one translational degree of freedom, wherein the kinematic chain comprises six circular cross-roller bearings (211, 212, 213, 214, 215, 216, 410, 510), wherein in the kinematic chain each two adjacent circular cross-roller bearings (211, 212)(212, 213)(213, 214)(214, 215)(215, 216)(410, 420) are more or less perpendicularly aligned and connected to each other such that the six circular cross-roller bearings form a stacked serial kinematic chain arrangement, wherein each of the circular cross-roller bearings have an inner ring and an outer ring wherein the two adjacent circular cross-roller bearings (211, 212)(212, 213)(213, 214)(214, 215)(215, 216)(410, 420) are rigidly connected to each other through a rigid connection element allowing the two adjacent cross-roller bearings to move with respect to each other connecting the inner ring of the first circular cross-roller bearing to the outer ring of the second circular cross-roller bearing in the more or less perpendicularly alignment, and wherein the serial kinematic chain is extended by one or two linear cross-roller bearings (221, 222) adding a translation degree of freedom, wherein the one or two linear cross-roller bearings (221, 222) are connected to the inner ring of the top or last circular cross-roller bearing in the chain of six interconnected circular cross-roller bearings; and wherein the kinematic chain comprises six circular cross-roller bearings (211, 212, 213, 214, 215, 216, 410, 510), wherein in the kinematic chain each two adjacent circular cross-roller bearings (211, 212)(212, 213)(213, 214)(214, 215)(215, 216)(410, 420) are more or less perpendicularly aligned and connected to each other such that the six circular cross-roller bearings form a stacked serial kinematic chain arrangement, wherein each of the circular cross-roller bearings have an inner ring and an outer ring wherein the two adjacent circular cross-roller bearings (211, 212)(212, 213)(213, 214)(214, 215)(215, 216)(410, 420) are rigidly connected to each other through a rigid connection element allowing the two adjacent cross-roller bearings to move with respect to each other connecting the inner ring of the first circular cross-roller bearing to the outer ring of the second circular cross-roller bearing in the more or less perpendicularly alignment, and wherein the serial kinematic chain is extended by one or two linear cross-roller bearings (221, 222) adding a translation degree of freedom, wherein the one or two linear cross-roller bearings (221, 222) are connected to the inner ring of the top or last circular cross-roller bearing in the chain of six interconnected circular cross-roller bearings; and (b) an instrument mounted to the two linear cross-roller bearings,