diff --git a/euslisp/robot-assembler-viewer.l b/euslisp/robot-assembler-viewer.l
index bafd72b..9851de0 100644
--- a/euslisp/robot-assembler-viewer.l
+++ b/euslisp/robot-assembler-viewer.l
@@ -416,6 +416,7 @@
       (push (list (list :initial-parts t)
                   (list :parts-type (iparts . type))
                   (list :parts-name (send iparts :name))
+                  (list :servo-id (send iparts :servo-id)) ;; TODO: generalize this (servo-id -> e.g., parts-attributes), make gui for this
                   ) *attach-history*)
       (if *robot-name*
           (setq *current-robot* (make-robot-assembler-robot iparts :name *robot-name*))
@@ -567,6 +568,7 @@
                     (list :parts-name (send *current-parts* :name))
                     (list :parts-type (*current-parts* . type))
                     (list :parts-point (send *current-parts-point* :name))
+                    (list :servo-id (send *current-parts* :servo-id)) ;; TODO: generalize this (servo-id -> e.g., parts-attributes), make gui for this
                     (list :configuration (if use-config
                                              (if (derivedp use-config coordinates)
                                                  (write-coords-as-string use-config)
diff --git a/euslisp/robot-assembler.l b/euslisp/robot-assembler.l
index 35f4840..c78baeb 100644
--- a/euslisp/robot-assembler.l
+++ b/euslisp/robot-assembler.l
@@ -96,6 +96,7 @@
   (:active-fixed-points () nil)
   (:horns (&rest args) nil)
   (:active-horns () nil)
+  (:servo-id (&rest args) nil)
   (:find (name search-method &key ((:class cls)))
    (let ((res (send self search-method))) ;; type??
      (find-if #'(lambda (x) (eq name (send x :name))) res)
@@ -168,6 +169,7 @@
   (:horns (&rest args) nil)
   (:active-horns () nil)
   (:not-active-horns () nil)
+  (:servo-id (&rest args) nil)
   (:sensor-parts? () (if extra-data t))
   (:sensor-type? (tp)
    (if extra-data (some #'(lambda (exdata) (eq tp (send exdata :get :type))) extra-data)))
@@ -234,7 +236,8 @@
 (defclass roboasm-actuator
   :super roboasm-parts
   :slots (horns ;; list of roboasm-fixed-point // TODO: horns -> actuated-points
-          )
+          servo-id
+         )
   )
 (defmethod roboasm-actuator
   (:remove-point (pt)
@@ -257,6 +260,7 @@
    (remove-if #'(lambda (x) (send x :descendants)) horns))
   (:not-active-horns ()
    (remove-if-not #'(lambda (x) (send x :descendants)) horns))
+  (:servo-id (&optional (arg nil)) (if arg (setq servo-id arg) servo-id))
   )
 
 (defclass roboasm-robot
@@ -657,6 +661,7 @@
          (limit (send start-coords :limit))
          (vlimit (send start-coords :vlimit))
          (tqlimit (send start-coords :tqlimit))
+         (servo-id (send (send start-coords :parent) :servo-id))
          type-name
          )
      (if new-name (setq name new-name))
@@ -689,6 +694,7 @@
      (format strm "~A<joint name=\"~A\" type=\"~A\">~%" offset name type-name);; uniq name
      (format strm "~A   <parent link=\"~A\"/>~%" offset parent-name)
      (format strm "~A   <child link=\"~A\"/>~%"  offset child-name)
+     (format strm "~A   <servo id=\"~A\"/>~%"  offset (if servo-id servo-id -1))
      (when initial-angle ;; type check
        (case type
         (:rotational
@@ -1525,6 +1531,7 @@
                (p-point (cadr (assoc :parts-point plist)))
                (attach-point (cadr (assoc :robot-parts-point plist)))
                (config (cadr (assoc :configuration plist)))
+               (servo-id (cadr (assoc :servo-id plist)))
                (p (make-parts-from-key p-type p-name))
                r-p p-p
                )
@@ -1532,6 +1539,7 @@
               (progn
                 (setq r-p (send arobot :find attach-point :active-fixed-points))
                 (setq p-p (send p :find p-point :active-fixed-points))
+                (send p :servo-id servo-id) ;; set servo-id here // TODO: support more general attributes
                 ;;(setq r-p (find-if #'(lambda (x) (eq attach-point (send x :name))) (send arobot :active-fixed-points)))
                 ;;(setq p-p (find-if #'(lambda (x) (eq p-point (send x :name))) (send p :active-fixed-points)))
                 (cond