executing a first operation to bring a first object held by a hand of a robot arm of a robot into contact with a second object based on a first force control parameter for a force sensor, a tool center point being set on the hand;

detecting a contact state between the first object and the second object;

detecting a first position of the tool center point when the processor detects the contact state;

acquiring an external force value applied to the robot arm by executing a second operation different from the first operation on the robot with the hand, the first object being further pushed toward the second object while the first and second objects are in the contact state in the second operation;

detecting a second position of the tool center point when the processor ends the second operation;

acquiring information of external rigidity based on a function of the acquired external force value and a movement amount of the tool center point between the first and second positions; and

changing the first force control parameter to a second force control parameter based on the acquired information of the external rigidity,

wherein the second operation includes an operation to drive the robot arm to move the first object in first directions crossing second directions along which the first object is inserted into and pulled out from the second object.