Pneumatic artificial muscles (PAMs) have been widely used in actuation of medical devices due to their intrinsic compliance and high power to weight ratio features. However, the nonlinearity and time-varying nature of PAMs makes it challenging to maintain highperformance tracking control. In this paper, a High-Order Pseudo-Partial Derivative based Model-Free Adaptive Iterative Learning Controller (HOPPD-MFAILC) is proposed to achieve fast convergence speed. The dynamics of PAM is converted into a dynamic linearization model during iterations, meanwhile, a high-order estimation algorithm is designed to estimate the pseudo-partial derivative component of the linearization model by only utilizing the input and output data in previous iterations. The stability and convergence performance of the controller is verified through theoretical analysis. Simulation and experimental results on PAM demonstrate that the proposed HOPPD-MFA ILC can track the desired trajectory with improved convergence and tracking performance. Index Terms-Pneumatic artificial muscle, model-free adaptive control, iterative learning control, convergence. I. INTRODUCTION NEUMATIC artificial muscle (PAM) is a tube-like actuator that largely mimics biological human muscle functions [1]. Compared to traditional electrical motors and hydraulic actuators, the lightweight, high compliance and high power-to-weight ratio of PAMs [2] have fueled their popularity among assistive exoskeletons and rehabilitation robots, such as the upper limb exoskeleton series RUPERT [3] and the lower limb orthotics KAFO [4]. However, unlike the conventional actuators adopted in Lokomat [5] and ArmeoPower [6], the nonlinear and time-varying nature of PAMs may cause Manuscript

Using microdata from U.S. household surveys, I document that families with a financially sophisticated husband are more likely to participate in the stock market than those with a wife of equal financial sophistication. This pattern is best explained by gender identity norms, which constrain women's influence over intrahousehold financial decision-making. A randomized controlled experiment reveals that female identity hinders idea contribution by the wife. These findings underscore the roles of intrahousehold bargaining and traditional norms in shaping household financial decisions.IN THE ANTEBELLUM SOUTH, WOMEN were expected to "recognize their subordinate place and to be obedient to the head of the family" (Scott (1970)). More than a century later, gender inequality persists despite women's empowerment. To illustrate, while married women's labor force participation has surged from 2% to 73% over the past century (Fernández ( 2013)), female workers continue to face a gender pay gap of more than 20% (Blau and Kahn ( 2017)).* I am deeply indebted to my advisor, Henrik Cronqvist, for his invaluable guidance and constant support. I would also like to thank the editor, Wei Xiong, an anonymous associate editor, two anonymous referees, Jawad M.

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What explains substantial variation across countries in household stock market participation? Building on Ke (2018), I hypothesize that the prevailing gender norm in a country is an important cultural factor. In a cross-country analysis, I find that households in countries with strong gender norms are less likely to participate in the stock market. In addition, I present suggestive evidence that gender role attitudes help explain cross-country differences in participation among the wealthy. My findings underscore the role of social norms in shaping household balance sheets across countries.