update readme

README.md

@@ -34,3 +34,15 @@ lb = -ub
 the success rates for **qp-based ik** and **realman Algo ik** are **76%** and **51%**.\
 At least one solver works out the ik, rate = **84%**.
 
+### update(1st July 2026)
+
+In each iteration, update optimization formula:
+
+- new cost item for distance from middle of the joint range. 
+- set up different weight for different joints motion.
+
+<img src="img/optimization.png" alt="Cost" width="400">
+
+<img src="img/cons.png" alt="Cost" width="400">
+
+<img src="img/osqp.png" alt="Cost" width="400">